SONUS PHARMACEUTICALS INC
8-A12G, 1996-08-23
IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES
Previous: RESIDENTIAL ACCREDIT LOANS INC, 8-K, 1996-08-23
Next: SONUS PHARMACEUTICALS INC, 8-K, 1996-08-23



<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                    FORM 8-A

                FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES
                     PURSUANT TO SECTION 12(b) OR (g) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

                           SONUS PHARMACEUTICALS, INC.
             (Exact name of registrant as specified in its charter)


      Delaware                                           95-4343413
(State of incorporation or organization)              (I.R.S. Employer
                                                     Identification No.)


22026 20th Avenue, S.E., Suite 102, Bothell, WA            98021
(Address of principal executive offices)                (Zip Code)


Securities to be registered pursuant to Section 12(b) of the Act:


Title of each class                    Name of each exchange on which
to be so registered                    each class is to be registered

         None                                      Not Applicable


Securities to be registered pursuant to Section 12(g) of the Act:


                               Rights to Purchase
                  Series A Junior Participating Preferred Stock
                                (Title of Class)
<PAGE>   2
Item 1.  Description of Registrant's Securities to be Registered

         On July 29, 1996, the Board of Directors of SONUS Pharmaceuticals, Inc.
(the "Corporation") approved the adoption of a Shareholder Rights Plan and on
September 3, 1996 declared a dividend distribution of one Right for each
outstanding share of the Corporation's Common Stock to stockholders of record on
the close of business on August 23, 1996 (the "Dividend Date"). Each Right
entitles the registered holder to purchase from the Corporation a unit
consisting of one one-hundredth of a share (a "Unit") of Series A Junior
Participating Preferred Stock, par value $0.001 per share (the "Preferred
Stock"), at a purchase price of $140 per Unit, subject to adjustment. The
description and terms of the Rights are set forth in a Rights Agreement (the
"Rights Agreement") between the Corporation and U.S. Stock Transfer Corporation,
as Rights Agent.

                  CERTIFICATES. Initially, the Rights will be attached to all
Common Stock certificates representing shares then outstanding, and no separate
Rights Certificates will be distributed. Subject to extension by the Board of
Directors in certain circumstances, the Rights will separate from the Common
Stock and a distribution date (the "Distribution Date") will occur upon the
earlier of (i) 10 days following a public announcement that a person or group of
affiliated or associated persons (an "Acquiring Person") has acquired, or
obtained the right to acquire, beneficial ownership of 15% or more of the
outstanding shares of Common Stock (the "Stock Acquisition Date"); or (ii) 10
business days following the commencement of a tender offer or exchange offer
that would result in a person or group beneficially owning 15% or more of the
outstanding shares of Common Stock. Current 15% stockholders are excluded from
the definition of an Acquiring Person until their respective beneficial
ownership exceeds 30% or more of the outstanding shares of Common Stock. Until
the Distribution Date, (i) the Rights will be evidenced by the Common Stock
certificates and will be transferred with and only with such Common Stock
certificates; (ii) new Common Stock certificates issued will contain a notation
incorporating the Rights Agreement by reference; and (iii) the surrender for
transfer of any certificates for Common Stock outstanding will also constitute
the transfer of the Rights associated with the Common Stock represented by such
certificate.


                  EXPIRATION AND EXERCISE. The Rights are not exercisable until
the Distribution Date and will expire at the close of business on August 23,
2006, unless earlier redeemed by the Corporation as described below.

                  As soon as practicable after the Distribution Date, Rights
Certificates will be mailed to holders of record of the Common Stock as of the
close of business on the Distribution Date and, thereafter, the separate Rights
Certificates will represent the Rights. Except as otherwise determined by the
Board of Directors, only shares of Common Stock issued prior to the Distribution
Date will be issued with Rights.

                  "FLIP-IN". In the event that, at any time following the
Dividend Date, (i) the Corporation is the surviving corporation in a merger with
an Acquiring Person and its Common Stock is not changed or exchanged; (ii) an
Acquiring Person becomes the beneficial owner of more than 15% of the
outstanding shares of Common Stock; (iii) an Acquiring Person engages in one or
more "self-dealing" transactions as set forth in the Rights Agreement; or (iv)
during such time as there is an Acquiring Person, an event occurs which results
in such Acquiring Person's ownership interest being increased by more than 1%
(e.g., a reverse stock split), each holder of a Right will thereafter have the
right to receive, upon exercise, Common Stock (or, in certain circumstances,


                                        2
<PAGE>   3
cash, property or other securities of the Corporation) having a value equal to
two times the exercise price of the Right. Notwithstanding any of the foregoing,
following the occurrence of any of the events set forth in this paragraph, all
Rights that are, or (under certain circumstances specified in the Rights
Agreement) were, beneficially owned by any Acquiring Person will be null and
void. However, Rights are not exercisable following the occurrence of any of the
events set forth above until such time as the Rights are no longer redeemable by
the Corporation as set forth below.

                  For example, at an exercise price of $140 per Right, each
Right not owned by an Acquiring Person (or by certain related parties) following
an event set forth in the preceding paragraph would entitle its holder to
purchase $280 worth of Common Stock (or other consideration, as noted above) for
$140. Assuming that the Common Stock had a per share value of $40 at such time,
the holder of each valid Right would be entitled to purchase 7 shares of Common
Stock for $140.

                  PERMITTED OFFER. A tender or exchange offer for all
outstanding Common Stock at a price and on terms determined by the Board of
Directors prior to the purchase to be adequate and in the best interests of the
Corporation and its stockholders (other than the Acquiring Person) is a
Permitted Offer under the Rights Agreement. A Permitted Offer does not trigger
the exercisability of the Rights.

                  "FLIP-OVER". In the event that, at any time following the
Stock Acquisition Date, (i) the Corporation is acquired in a merger or other
business combination transaction in which the Corporation is not the surviving
corporation; or (ii) 50% or more of the Corporation's assets or earning power is
sold or transferred, each holder of a Right (except Rights which previously have
been voided as set forth above) shall thereafter have the right to receive, upon
exercise, common stock of the acquiring company having a value equal to two
times the exercise price of the Right. The events set forth in this paragraph
and in the third preceding paragraph are referred to as the "Triggering Events."

                  EXCHANGE FEATURE. At any time after any Person becomes an
Acquiring Person and prior to the acquisition by such person or group of 50% or
more of the outstanding Common Stock, the Board of Directors may exchange the
Rights (other than Rights owned by such Person or group which will have become
void), in whole or in part, at an exchange rate of one share of Common Stock (or
a combination of cash, property, Common Stock or other securities having an
equal value) per Right (subject to adjustment).

                  ADJUSTMENT FOR DILUTION. The purchase price payable, and the
number of Units of Preferred Stock or other securities or property issuable upon
exercise of the Rights are subject to adjustment from time to time to prevent
dilution (i) in the event of a stock dividend on, or a subdivision, combination
or reclassification of, the Preferred Stock; (ii) if holders of the Preferred
Stock are granted certain rights or warrants to subscribe for Preferred Stock or
convertible securities at less than the current market price of the Preferred
Stock; or (iii) upon the distribution to holders of the Preferred Stock of
evidences of indebtedness or assets (excluding regular quarterly cash dividends)
or of subscription rights or warrants (other than those referred to above).

                  With certain exceptions, no adjustment in the purchase price
will be required until cumulative adjustments amount to at least 1% of the
purchase price. No fractional Units will be


                                        3
<PAGE>   4
issued and, in lieu thereof, an adjustment in cash will be made based on the
market price of the Preferred Stock on the last trading date prior to the date
of exercise.

                  REDEMPTION. At any time until ten days following the Stock
Acquisition Date (subject to extension by the Continuing Directors, as defined
below), the Corporation may redeem the Rights in whole, but not in part, at a
price of $.01 per Right. Under certain circumstances set forth in the Rights
Agreement, the decision to redeem shall require the concurrence of a majority of
the Continuing Directors. After the redemption period has expired, the
Corporation's right of redemption may be reinstated if an Acquiring Person
reduces his beneficial ownership to 15% or less of the outstanding shares of the
Common Stock in a transaction or series of transactions not involving the
Corporation. Immediately upon the action of the Board of Directors ordering
redemption of the Rights, with (where required) the concurrence of the
Continuing Directors, the Rights will terminate and the only right of the
holders of Rights will be to receive the $.01 redemption price. Rights are not
exercisable while subject to redemption.

                  CONTINUING DIRECTORS. The term "Continuing Directors" means
any member of the Board of Directors of the Corporation who was a member of the
Board prior to the date of the Rights Agreement, and any person who is
subsequently elected to the Board if such person is recommended or approved by a
majority of the Continuing Directors, but shall not include an Acquiring Person,
or an affiliate or associate of an Acquiring Person, or any representative of
the foregoing entities.

                  STOCKHOLDER RIGHTS. Until a Right is exercised, the holder
thereof, as such, will have no rights as a stockholder of the Corporation,
including, without limitation, the right to vote or to receive dividends. While
the distribution of the Rights will not be taxable to stockholders or to the
Corporation, stockholders may, depending upon the circumstances, recognize
taxable income in the event that the Rights become exercisable for Common Stock
(or other consideration) of the Corporation or for common stock of the acquiring
company as set forth above.

                  AMENDMENTS. Any of the provisions of the Rights Agreement may
be amended by the Board of Directors of the Corporation prior to the
Distribution Date. After the Distribution Date, the provisions of the Rights
Agreement may be amended by the Board (in certain circumstances, with the
concurrence of the Continuing Directors) in order to cure any ambiguity, to make
changes which do not adversely affect the interests of holders of Rights
(excluding the interests of any Acquiring Person), or to shorten or lengthen any
time period under the Rights Agreement; provided, however, that no amendment to
adjust the time period governing redemption shall be made at such time as the
Rights are not redeemable.

Item 2.  Exhibits

1.       Rights Agreement, dated as of August 23, 1996 between SONUS
         Pharmaceuticals, Inc. and U.S. Stock Transfer Corporation, which
         includes as Exhibit A thereto a form of Certificate of Designation for
         the Preferred Stock, as Exhibit B thereto the Form of Rights
         Certificate and as Exhibit C thereto a Summary of Terms of Shareholder
         Rights Plan. Rights Certificates will not be mailed until after the
         Distribution Date (as that term is defined in the Rights Agreement).


                                        4
<PAGE>   5
                                    SIGNATURE

         Pursuant to the requirements of Section 12 of the Securities Exchange
Act of 1934, the registrant has duly caused this registration statement to be
signed on its behalf by the undersigned, thereto duly authorized.


Date:  August 23, 1996            SONUS Pharmaceuticals, Inc.



                                  By:  /s/ Steven C. Quay, M.D., Ph.D.
                                       ---------------------------------------
                                       Steven C. Quay, M.D., Ph.D., President
                                       and Chief Executive Officer


                                        5
<PAGE>   6
                                 EXHIBIT INDEX




 Exhibit                                                             Sequential
  Number                         Description                          Page No. 
 -------                         -----------                         ----------

    1   Rights Agreement, dated as of August 23, 1996 between              7
        SONUS Pharmaceuticals, Inc. and U.S. Stock Transfer
        Corporation, which includes as Exhibit A thereto a form of
        Certificate of Designation for the Preferred Stock, as Exhibit
        B thereto the Form of Rights Certificate and as Exhibit C
        thereto a Summary of Terms of Shareholder Rights Plan.


                                        6

<PAGE>   1
                                                                       Exhibit 1


                           SONUS PHARMACEUTICALS, INC.

                                       and

                         U.S. STOCK TRANSFER CORPORATION

                                  Rights Agent



                                Rights Agreement
                           Dated as of August 23, 1996
<PAGE>   2
                                TABLE OF CONTENTS


<TABLE>
<S>             <C>                                                                                              <C>
Section 1.      Certain Definitions.............................................................................  1

Section 2.      Appointment of Rights Agent.....................................................................  4

Section 3.      Issue of Rights Certificates....................................................................  5

Section 4.      Form of Rights Certificates.....................................................................  6

Section 5.      Countersignature and Registration...............................................................  7

Section 6.      Transfer, Split Up, Combination and Exchange of Rights Certificates;
                  Mutilated, Destroyed, Lost or Stolen Rights Certificates......................................  8

Section 7.      Exercise of Rights; Purchase Price; Expiration Date of Rights...................................  8

Section 8.      Cancellation and Destruction of Rights Certificates............................................. 10

Section 9.      Reservation and Availability of Capital Stock................................................... 10

Section 10.     Preferred Stock Record Date..................................................................... 12

Section 11.     Adjustment of Purchase Price, Number and Kind of Shares or Number of
                  Rights........................................................................................ 12

Section 12.     Certificate of Adjusted Purchase Price or Number of Shares...................................... 20

Section 13.     Consolidation, Merger or Sale or Transfer of Assets or Earning Power............................ 20

Section 14.     Fractional Rights and Fractional Shares......................................................... 23

Section 15.     Rights of Action................................................................................ 24

Section 16.     Agreement of Rights Holders..................................................................... 24

Section 17.     Rights Certificate Holder Not Deemed a Stockholder.............................................. 25

Section 18.     Concerning the Rights Agent..................................................................... 25

Section 19.     Merger or Consolidation or Change of Name of Rights Agent....................................... 25

Section 20.     Duties of Rights Agent.......................................................................... 26

Section 21.     Change of Rights Agent.......................................................................... 27

Section 22.     Issuance of New Rights Certificates............................................................. 28
</TABLE>


                                        i
<PAGE>   3
<TABLE>
<S>             <C>                                                                                              <C>
Section 23.     Redemption...................................................................................... 29

Section 24.     Exchange........................................................................................ 30

Section 25.     Notice of Certain Events........................................................................ 31

Section 26.     Notices......................................................................................... 32

Section 27.     Supplements and Amendments...................................................................... 33

Section 28.     Successors...................................................................................... 33

Section 29.     Determinations and Actions by the Board of Directors, etc....................................... 33

Section 30.     Benefits of this Agreement...................................................................... 34

Section 31.     Severability.................................................................................... 34

Section 32.     Governing Law................................................................................... 34

Section 33.     Counterparts.................................................................................... 34

Section 34.     Descriptive Headings............................................................................ 34
</TABLE>


EXHIBITS

Exhibit A       Form of Certificate of Designation, Preferences and Rights
Exhibit B       Form of Rights Certificate
Exhibit C       Summary of Terms


                                       ii
<PAGE>   4
                                RIGHTS AGREEMENT



         RIGHTS AGREEMENT, dated as of August 23, 1996 (the "Agreement"),
between SONUS Pharmaceuticals, Inc., a Delaware corporation (the "Company"), and
U.S. STOCK TRANSFER CORPORATION (the "Rights Agent").


                              W I T N E S S E T H :

         WHEREAS, on July 29, 1996 (the "Rights Dividend Declaration Date"), the
Board of Directors of the Company authorized and declared a dividend
distribution of one Right for each share of Common Stock, par value $.001 per
share, of the Company outstanding at the close of business on August 23, 1996
(the "Record Date"), and has authorized the issuance of one Right (as such
number may hereinafter be adjusted pursuant to the provisions of Section 11(p)
hereof) for each share of Common Stock of the Company issued between the Record
Date (whether originally issued or delivered from the Company's treasury) and
the Distribution Date (as defined in Section 3 hereof), each Right initially
representing the right to purchase one one-hundredth of a share of Series A
Junior Participating Preferred Stock of the Company, $.001 par value, having the
rights, powers and preferences set forth in the form of Certificate of
Designation, Preferences and Rights attached hereto as Exhibit A, upon the terms
and subject to the conditions hereinafter set forth (the "Rights");

         NOW, THEREFORE, in consideration of the premises and the mutual
agreements herein set forth, the parties hereby agree as follows:

         SECTION 1. CERTAIN DEFINITIONS. For purposes of this Agreement, the
following terms have the meanings indicated:

                  (a) "Acquiring Person" shall mean any Person who or which,
together with all Affiliates and Associates of such Person, shall be the
Beneficial Owner of 15% or more of the shares of Common Stock then outstanding,
but shall not include (i) the Company, any Subsidiary of the Company, any
employee benefit plan of the Company or of any Subsidiary of the Company, or any
Person or entity organized, appointed or established by the Company for or
pursuant to the terms of any such plan, (ii) any Person who shall become the
Beneficial Owner of 15% or more of the outstanding shares of Common Stock solely
as a result of an acquisition by the Company of shares of Common Stock until
such time thereafter as such Person shall become the Beneficial Owner (other
than by means of a stock dividend or stock split) of any additional shares of
Common Stock or (iii) Steven C. Quay, M.D. Ph.D., Debra L. Quay, and/or any
trust or estate planning device into which such shares may be transferred,
unless Steven C. Quay M.D., Ph.D., Debra L. Quay, and/or any trust estate
planning device into which such shares may be transferred, shall be the
Beneficial Owner of 30% or more of the shares of Common Stock then outstanding.
In addition, notwithstanding the foregoing, no Person shall be deemed to be an
Acquiring Person either (i) if the Board of Directors of the Company determines
in good faith that a person who would otherwise be an "Acquired Person" (but for
the operation of this clause (i)), has become such inadvertently, and such
person divests as promptly as practical a sufficient number of shares of Common
Stock so that such person would no longer be an "Acquiring Person," or (ii) as
the result of an acquisition of Common Stock by the Company which, by reducing
the number of shares outstanding, increases the proportionate


                                       1
<PAGE>   5
number of shares beneficially owned by such Person to 15% or more of the Common
Stock of the Company then outstanding; provided, however, that if a Person shall
become the Beneficial Owner of 15% or more of the Common Stock of the Company
then outstanding by reason of share purchases by the Company and shall, after
such share purchases by the Company, become the Beneficial Owner of any
additional Common Stock of the Company, then such Person shall be deemed to be
an Acquiring Person.

                  (b) "Affiliate" and "Associate" shall have the respective
meanings ascribed to such terms in Rule 12b-2 of the General Rules and
Regulations under the Exchange Act, as in effect on the date of this Agreement.

                  (c) A Person shall be deemed the "Beneficial Owner" of, and
shall be deemed to "beneficially own," any securities:

                           (i) which such Person or any of such Person's
         Affiliates or Associates beneficially owns, directly or indirectly;

                           (ii) which such Person or any of such Person's
         Affiliates or Associates, directly or indirectly, has the right to
         acquire (whether such right is exercisable immediately or only after
         the passage of time) pursuant to any agreement, arrangement or
         understanding (whether or not in writing) or upon the exercise of
         conversion rights, exchange rights, rights, warrants or options, or
         otherwise; provided, however, that a Person shall not be deemed the
         "Beneficial Owner" of, or to "beneficially own," (A) securities
         tendered pursuant to a tender or exchange offer made by such person or
         any of such Person's Affiliates or Associates until such tendered
         securities are accepted for purchase or exchange, or (B) securities
         which a Person or any of such Person's Affiliates or Associates may be
         deemed to have the right to acquire pursuant to any merger or other
         acquisition agreement between the Company and such Person (or one or
         more of its Affiliates or Associates) if such agreement has been
         approved by the Board of Directors of the Company prior to there being
         an Acquiring Person, or (C) securities issuable upon exercise of Rights
         at any time prior to the occurrence of a Triggering Event, or (D)
         securities issuable upon exercise of Rights from and after the
         occurrence of a Triggering Event which Rights were acquired by such
         Person or any of such Person's Affiliates or Associates prior to the
         Distribution Date or pursuant to Section 3(a) or Section 22 hereof (the
         "Original Rights") or pursuant to Section 11(i) hereof in connection
         with an adjustment made with respect to any Original Rights;

                           (iii) which such Person or any of such Person's
         Affiliates or Associates, directly or indirectly, has the right to vote
         or dispose of or "beneficial ownership" of (as determined pursuant to
         Rule 13d-3 of the General Rules and Regulations under the Exchange
         Act), including pursuant to any agreement, arrangement or
         understanding, whether or not in writing; provided, however, that a
         Person shall not be deemed the "Beneficial Owner" of, or to
         "beneficially own," any security under this subparagraph (ii) as a
         result of an agreement, arrangement or understanding to vote such
         security if such agreement, arrangement or understanding: (A) arises
         solely from a revocable proxy given in response to a public proxy or
         consent solicitation made pursuant to, and in accordance with, the
         applicable provisions of the General Rules and Regulations under the
         Exchange Act, and (B) is not also then reportable by such Person on
         Schedule 13D under the Exchange Act (or any comparable or successor
         report); or


                                       2
<PAGE>   6
                           (iv) which are beneficially owned, directly or
         indirectly, by any other Person (or any Affiliate or Associate thereof)
         with which such Person (or any of such Person's Affiliates or
         Associates) has any agreement, arrangement or understanding (whether or
         not in writing), for the purpose of acquiring, holding, voting (except
         pursuant to a revocable proxy as described in the proviso to
         subparagraph (ii) of this paragraph (c)) or disposing of any voting
         securities of the Company; provided, however, that nothing in this
         paragraph (c) shall cause a person engaged in business as an
         underwriter of securities to be the "Beneficial Owner" of, or to
         "beneficially own," any securities acquired through such person's
         participation in good faith in a firm commitment underwriting until the
         expiration of forty days after the date of such acquisition; and
         provided further, however, that in no case shall an officer or director
         of the Company be deemed (x) the Beneficial Owner of any securities
         beneficially owned by another officer or director of the Company solely
         by reason of actions undertaken by such persons in their capacity as
         officers or directors of the Company or (y) the Beneficial Owner of
         securities held of record by the trustee of any employee benefit plan
         of the Company or any Subsidiary of the Company for the benefit of any
         employee of the Company or any Subsidiary of the Company, other than
         the officer or director, by reason of any influence that such officer
         or director may have over the voting of the securities held in the
         plan.

                  (d) "Business Day" shall mean any day other than a Saturday,
Sunday or a day on which banking institutions in the State of California is
authorized or obligated by law or executive order to close.

                  (e) "Close of business" on any given date shall mean 5:00
P.M., California time, on such date; provided, however, that if such date is not
a Business Day it shall mean 5:00 P.M., California time, on the next succeeding
Business Day.

                  (f) "Common Stock" shall mean the Common Stock, par value
$.0025 per share, of the Company, except that "Common Stock" when used with
reference to any Person other than the Company shall mean the capital stock of
such Person with the greatest voting power, or the equity securities or other
equity interest having power to control or direct the management, of such
Person.

                  (g) "Continuing Director" shall mean (i) any member of the
Board of Directors of the Company, while such Person is a member of the Board,
who is not an Acquiring Person, or an Affiliate or Associate of an Acquiring
Person, or a representative of an Acquiring Person or of any such Affiliate or
Associate, and was a member of the Board prior to the date of this Agreement, or
(ii) any Person who subsequently becomes a member of the Board, while such
Person is a member of the Board, who is not an Acquiring Person, or an Affiliate
or Associate of an Acquiring Person, or a representative of an Acquiring Person
or of any such Affiliate or Associate, if such Person's nomination for election
or election to the Board is recommended or approved by a majority of the
Continuing Directors.

                  (h) "Expiration Date" shall mean the earliest of (i) the close
of business on the Final Expiration Date, (ii) the time at which the Rights are
redeemed as provided in Section 23 hereof, (iii) the time at which the Board of
Directors orders the exchange of the Rights as provided in Section 24 hereof, or
(iv) the consummation of a transaction contemplated by Section 13(d) hereof.


                                       3
<PAGE>   7
                  (i) "Final Expiration Date" shall mean August 23, 2006.


                  (j) "Person" shall mean any individual, firm, corporation,
partnership or other entity, and shall include any successor (by merger or
otherwise) of such entity.

                  (k) "Permitted Offer" shall mean a tender offer for all
outstanding Common Stock made in the manner prescribed by Section 14(d) of the
Exchange Act and the rules and regulations promulgated thereunder; provided,
however, that such tender offer occurs at a time when Continuing Directors are
in office and a majority of the Continuing Directors then in office has
determined that the offer is both adequate and otherwise in the best interests
of the Company and its stockholders (taking into account all factors that such
Continuing Directors deem relevant, including, without limitation, prices that
could reasonably be achieved if the Company or its assets were sold on an
orderly basis designed to realize maximum value).

                  (l) "Preferred Stock" shall mean shares of Series A Junior
Participating Preferred Stock, $.001 per share par value, of the Company, having
the rights and preferences set forth in the form of Certificate of Designations,
Preferences and Rights attached hereto as Exhibit A.

                  (m) "Section 11(a)(ii) Event" shall mean any event described
in Section 11(a)(ii) (A), (B) or (C) hereof.

                  (n) "Section 13 Event" shall mean any event described in
clauses (x), (y) or (z) of Section 13(a) hereof.

                  (o) "Stock Acquisition Date" shall mean the first date of
public announcement (which, for purposes of this definition, shall include,
without limitation, a report filed pursuant to Section 13(d) under the Exchange
Act) by the Company or an Acquiring Person that an Acquiring Person has become
such.

                  (p) "Subsidiary" shall mean, with reference to any Person, any
corporation of which an amount of voting securities sufficient to elect at least
a majority of the directors of such corporation is beneficially owned, directly
or indirectly, by such Person, or otherwise controlled by such person.

                  (q) "Triggering Event" shall mean any Section 11(a)(ii) Event
or any Section 13 Event.

         SECTION 2. APPOINTMENT OF RIGHTS AGENT. The Company hereby appoints the
Rights Agent to act as agent for the Company and the holders of the Rights (who,
in accordance with Section 3 hereof, shall prior to the Distribution Date also
be the holders of the Common Stock) in accordance with the terms and conditions
hereof, and the Rights Agent hereby accepts such appointment. The Company may
from time to time appoint such Co-Rights Agents as it may deem necessary or
desirable.


                                       4
<PAGE>   8
         SECTION 3. ISSUE OF RIGHTS CERTIFICATES.

                  (a) Until the earlier of (i) the close of business on the
tenth day (or such later date as may be determined by action of a majority of
Continuing Directors then in office) after the Stock Acquisition Date (or, if
the tenth day after the Stock Acquisition Date occurs before the Record Date,
the close of business on the Record Date), or (ii) the close of business on the
tenth Business Day (or such later date as may be determined by action of a
majority of Continuing Directors then in office) after the date that a tender or
exchange offer by any Person (other than the Company, any Subsidiary of the
Company, any employee benefit plan of the Company or of any Subsidiary of the
Company, or any Person or entity organized, appointed or established by the
Company for or pursuant to the terms of any such plan) is first published or
sent or given within the meaning of Rule 14d-2(a) of the General Rules and
Regulations under the Exchange Act, if upon consummation thereof, such Person
would be the Beneficial Owner of 15% or more of the shares of Common Stock then
outstanding (the earlier of (i) and (ii) being herein referred to as the
"Distribution Date"), (x) the Rights will be evidenced (subject to the
provisions of paragraph (b) of this Section 3) by the certificates for the
Common Stock registered in the names of the holders of the Common Stock (which
certificates for Common Stock shall be deemed also to be certificates for
Rights) and not by separate certificates, and (y) the Rights will be
transferable only in connection with the transfer of the underlying shares of
Common Stock (including a transfer to the Company). As soon as practicable after
the Distribution Date, the Rights Agent will send by first-class, insured,
postage prepaid mail, to each record holder of the Common Stock as of the close
of business on the Distribution Date, at the address of such holder shown on the
records of the Company, one or more rights certificates, in substantially the
form of Exhibit B hereto (the "Rights Certificates"), evidencing one Right for
each share of Common Stock so held, subject to adjustment as provided herein. In
the event that an adjustment in the number of Rights per share of Common Stock
has been made pursuant to Section 11(p) hereof, at the time of distribution of
the Rights Certificates, the Company shall make the necessary and appropriate
rounding adjustments (in accordance with Section 14(a) hereof) so that Rights
Certificates representing only whole numbers of Rights are distributed and cash
is paid in lieu of any fractional Rights. As of and after the Distribution Date,
the Rights will be evidenced solely by such Rights Certificates and may be
transferred by the transfer of the Rights Certificates as permitted hereby,
separately and apart from any transfer of one or more Common Stock, and the
holders of such Rights Certificates as listed in the records of the Company or
any transfer agent or registrar for the Rights shall be the record holders
thereof.

                  (b) As promptly as practicable following the Record Date, the
Company will send a copy of a Summary of Rights, in substantially the form
attached hereto as Exhibit C (the "Summary of Rights"), by first-class, postage
prepaid mail, to each record holder of the Common Stock as of the close of
business on the Record Date, at the address of such holder shown on the records
of the Company. With respect to certificates for the Common Stock outstanding as
of the Record Date, until the Distribution Date, the Rights will be evidenced by
such certificates for the Common Stock and the registered holders of the Common
Stock shall also be the registered holders of the associated Rights. Until the
earlier of the Distribution Date or the Expiration Date, the transfer of any
certificates representing shares of Common Stock in respect of which Rights have
been issued shall also constitute the transfer of the Rights associated with
such shares of Common Stock.

                  (c) Unless the Board of Directors by resolution adopted at or
before the time of the issuance (including pursuant to the exercise of rights
under the Company's benefit plans) of any


                                       5
<PAGE>   9
Common Stock specifies to the contrary, Rights shall be issued in respect of all
shares of Common Stock which are issued after the Record Date but prior to the
earlier of the Distribution Date or the Expiration Date. Certificates
representing such shares of Common Stock shall also be deemed to be certificates
for Rights, and shall bear the following legend:

                  This certificate also evidences and entitles the holder hereof
         to certain Rights as set forth in the Rights Agreement between SONUS
         Pharmaceuticals, Inc., a Delaware corporation (the "Company") and U.S.
         Stock Transfer Corporation (the "Rights Agent"), dated as of August 23,
         1996 (the "Rights Agreement"), the terms of which are hereby
         incorporated herein by reference and a copy of which is on file at the
         principal offices of the Company. Under certain circumstances, as set
         forth in the Rights Agreement, such Rights will be evidenced by
         separate certificates and will no longer be evidenced by this
         certificate. The Company will mail to the holder of this certificate a
         copy of the Rights Agreement, as in effect on the date of mailing,
         without charge promptly after receipt of a written request therefor.
         Under certain circumstances set forth in the Rights Agreement, Rights
         issued to, or held by, any Person who is, was or becomes an Acquiring
         Person or any Affiliate or Associate thereof (as such terms are defined
         in the Rights Agreement), whether currently held by or on behalf of
         such Person or by any subsequent holder, may become null and void.

With respect to such certificates containing the foregoing legend, until the
earlier of (i) the Distribution Date or (ii) the Expiration Date, the Rights
associated with the Common Stock represented by such certificates shall be
evidenced by such certificates alone and registered holders of Common Stock
shall also be the registered holders of the associated Rights, and the transfer
of any of such certificates shall also constitute the transfer of the Rights
associated with the Common Stock represented by such certificates. In the event
that the Company purchases or acquires any Common Stock after the Record Date
but prior to the Distribution Date, any Rights associated with such Common Stock
shall be deemed cancelled and retired so that the Company shall not be entitled
to exercise any Rights associated with the Common Stock which are no longer
outstanding.

         SECTION 4. FORM OF RIGHTS CERTIFICATES.

                  (a) The Rights Certificates (and the forms of election to
purchase and of assignment to be printed on the reverse thereof) shall each be
substantially in the form set forth in Exhibit B hereto and may have such marks
of identification or designation and such legends, summaries or endorsements
printed thereon as the Company may deem appropriate and as are not inconsistent
with the provisions of this Agreement, or as may be required to comply with any
applicable law or with any rule or regulation made pursuant thereto or with any
rule or regulation of any stock exchange on which the Rights may from time to
time be listed, or to conform to usage. Subject to the provisions of Section 11
and Section 22 hereof, the Rights Certificates, whenever distributed, shall be
dated as of the Record Date and on their face shall entitle the holders thereof
to purchase such number of one one-hundredths of a share of Preferred Stock as
shall be set forth therein at the price set forth therein (such exercise price
per one one-hundredth of a share, the "Purchase Price"), but the amount and type
of securities purchasable upon the exercise of each Right and the Purchase Price
thereof shall be subject to adjustment as provided herein.


                                       6
<PAGE>   10
                  (b) Any Rights Certificate issued pursuant to Section 3(a) or
Section 22 hereof that represents Rights beneficially owned by: (i) an Acquiring
Person or any Associate or Affiliate of an Acquiring Person, (ii) a transferee
of an Acquiring Person (or of any such Associate or Affiliate) who becomes a
transferee after the Acquiring Person becomes such, or (iii) a transferee of an
Acquiring Person (or of any such Associate or Affiliate) who becomes a
transferee prior to or concurrently with the Acquiring Person becoming such and
receives such Rights pursuant to either (A) a transfer (whether or not for
consideration) from the Acquiring Person to holders of equity interests in such
Acquiring Person or to any Person with whom such Acquiring Person has any
continuing agreement, arrangement or understanding regarding the transferred
Rights or (B) a transfer which the Board of Directors of the Company has
determined is part of a plan, arrangement or understanding which has as a
primary purpose or effect avoidance of Section 7(e) hereof, and any Rights
Certificate issued pursuant to Section 6 or Section 11 hereof upon transfer,
exchange, replacement or adjustment of any other Rights Certificate referred to
in this sentence, shall contain (to the extent feasible) the following legend:

         The Rights represented by this Rights Certificate are or were
         beneficially owned by a Person who was or became an Acquiring Person or
         an Affiliate or Associate of an Acquiring Person (as such terms are
         defined in the Rights Agreement). Accordingly, this Rights Certificate
         and the Rights represented hereby may become null and void in the
         circumstances specified in Section 7(e) of such Agreement.

         SECTION 5. COUNTERSIGNATURE AND REGISTRATION.

                  (a) The Rights Certificates shall be executed on behalf of the
Company by its Chairman of the Board, its President or any Vice President,
either manually or by facsimile signature, and shall have affixed thereto the
Company's seal or a facsimile thereof which shall be attested by the Secretary
or an Assistant Secretary of the Company, either manually or by facsimile
signature. The Rights Certificates shall be manually countersigned by the Rights
Agent and shall not be valid for any purpose unless so countersigned. In case
any officer of the Company who shall have signed any of the Rights Certificates
shall cease to be such officer of the Company before countersignature by the
Rights Agent and issuance and delivery by the Company, such Rights Certificates,
nevertheless, may be countersigned by the Rights Agent and issued and delivered
by the Company with the same force and effect as though the person who signed
such Rights Certificates had not ceased to be such officer of the Company; and
any Rights Certificates may be signed on behalf of the Company by any person
who, at the actual date of the execution of such Rights Certificate, shall be a
proper officer of the Company to sign such Rights Certificate, although at the
date of the execution of this Rights Agreement any such person was not such an
officer.

                  (b) Following the Distribution Date, the Rights Agent will
keep or cause to be kept, at its principal office or offices designated as the
appropriate place for surrender of Rights Certificates upon exercise or
transfer, books for registration and transfer of the Rights Certificates issued
hereunder. Such books shall show the names and addresses of the respective
holders of the Rights Certificates, the number of Rights evidenced on its face
by each of the Rights Certificates, the Rights Certificate number and the date
of each of the Rights Certificates.


                                       7
<PAGE>   11
         SECTION 6. TRANSFER, SPLIT UP, COMBINATION AND EXCHANGE OF RIGHTS
CERTIFICATES; MUTILATED, DESTROYED, LOST OR STOLEN RIGHTS CERTIFICATES.

                  (a) Subject to the provisions of Section 4(b), Section 7(e),
Section 14 and Section 24 hereof, at any time after the close of business on the
Distribution Date, and at or prior to the close of business on the Expiration
Date, any Rights Certificate or Certificates may be transferred, split up,
combined or exchanged for another Rights Certificate or Certificates, entitling
the registered holder to purchase a like number of one one-hundredths of a share
of Preferred Stock (or following a Triggering Event, Common Stock, other
securities, cash or other assets, as the case may be) as the Rights Certificate
or Certificates surrendered then entitled such holder (or former holder in the
case of a transfer) to purchase. Any registered holder desiring to transfer,
split up, combine or exchange any Rights Certificate or Certificates shall make
such request in writing delivered to the Rights Agent, and shall surrender the
Rights Certificate or Certificates to be transferred, split up, combined or
exchanged at the principal office or offices of the Rights Agent designated for
such purpose. Neither the Rights Agent nor the Company shall be obligated to
take any action whatsoever with respect to the transfer of any such surrendered
Rights Certificate until the registered holder shall have completed and signed
the certificate contained in the form of assignment on the reverse side of such
Rights Certificate and shall have provided such additional evidence of the
identity of the Beneficial Owner (or former Beneficial Owner) or Affiliates or
Associates thereof as the Company shall reasonably request. Thereupon the Rights
Agent shall, subject to Section 4(b), Section 7(e), Section 14 and Section 24
hereof, countersign and deliver to the Person entitled thereto a Rights
Certificate or Rights Certificates, as the case may be, as so requested. The
Company may require payment of a sum sufficient to cover any tax or governmental
charge that may be imposed in connection with any transfer, split up,
combination or exchange of Rights Certificates.

                  (b) Upon receipt by the Company and the Rights Agent of
evidence reasonably satisfactory to them of the loss, theft, destruction or
mutilation of a Rights Certificate, and, in case of loss, theft or destruction,
of indemnity or security reasonably satisfactory to them, and reimbursement to
the Company and the Rights Agent of all reasonable expenses incidental thereto,
and upon surrender to the Rights Agent and cancellation of the Rights
Certificate if mutilated, the Company will execute and deliver a new Rights
Certificate of like tenor to the Rights Agent for countersignature and delivery
to the registered owner in lieu of the Rights Certificate so lost, stolen,
destroyed or mutilated.

                  SECTION 7. EXERCISE OF RIGHTS; PURCHASE PRICE; EXPIRATION DATE
OF RIGHTS.

                  (a) Subject to Section 7(e) hereof, the registered holder of
any Rights Certificate may exercise the Rights evidenced thereby (except as
otherwise provided herein including, without limitation, the restrictions on
exercisability set forth in Section 9(c), Section 11(a)(iii) and Section 23(a)
hereof) in whole or in part at any time after the Distribution Date upon
surrender of the Rights Certificate, with the form of election to purchase and
the certificate on the reverse side thereof duly executed, to the Rights Agent
at the principal office or offices of the Rights Agent designated for such
purpose, together with payment of the aggregate Purchase Price with respect to
the total number of one one-hundredths of a share (or other securities or
property, as the case may be) as to which such surrendered Rights are then
exercisable, at or prior to the Expiration Date.


                                       8
<PAGE>   12
                  (b) The Purchase Price for each one one-hundredth of a share
of Preferred Stock pursuant to the exercise of a Right shall initially be $140,
and shall be subject to adjustment from time to time as provided in Section 11
hereof and shall be payable in accordance with paragraph (c) below.

                  (c) Upon receipt of a Rights Certificate representing
exercisable Rights, with the form of election to purchase and the certificate
duly executed, accompanied by payment, with respect to each Right so exercised,
of the Purchase Price per one one-hundredth of a share of Preferred Stock (or
other shares, securities or property, as the case may be) to be purchased as set
forth below and an amount equal to any applicable transfer tax, the Rights Agent
shall, subject to Section 20(k) hereof, thereupon promptly (i) (A) requisition
from any transfer agent of the shares of Preferred Stock (or make available, if
the Rights Agent is the transfer agent for such shares) certificates for the
total number of one one-hundredths of a share of Preferred Stock to be purchased
and the Company hereby irrevocably authorizes its transfer agent to comply with
all such requests, or (B) if the Company shall have elected to deposit the total
number of shares of Preferred Stock issuable upon exercise of the Rights
hereunder with a depositary agent, requisition from the depositary agent
depositary receipts representing such number of one one-hundredths of a share of
Preferred Stock as are to be purchased (in which case certificates for the
shares of Preferred Stock represented by such receipts shall be deposited by the
transfer agent with the depositary agent) and the Company will direct the
depositary agent to comply with such request, (ii) requisition from the Company
the amount of cash, if any, to be paid in lieu of fractional shares in
accordance with Section 11 hereof, (iii) after receipt of such certificates or
depositary receipts, cause the same to be delivered to or upon the order of the
registered holder of such Rights Certificate, registered in such name or names
as may be designated by such holder, and (iv) after receipt thereof, deliver
such cash, if any, to or upon the order of the registered holder of such Rights
Certificate. The payment of the Purchase Price (as such amount may be reduced
pursuant to Section 11(a)(iii) hereof) may be made (x) in cash or by certified
bank check or money order payable to the order of the Company, or (y) by
delivery of a certificate or certificates (with appropriate stock powers
executed in blank attached thereto) evidencing a number of shares of Common
Stock equal to the then Purchase Price divided by the closing market price (as
determined pursuant to Section 11(d) hereof) per share of Common Stock on the
Trading Date immediately preceding the date of such exercise. In the event that
the Company is obligated to issue other securities (including Common Stock) of
the Company, pay cash and/or distribute other property pursuant to Section 11(a)
hereof, the Company will make all arrangements necessary so that such other
securities, cash and/or other property are available for distribution by the
Rights Agent, if and when appropriate.

                  (d) In case the registered holder of any Rights Certificate
shall exercise less than all the Rights evidenced thereby, a new Rights
Certificate evidencing Rights equivalent to the Rights remaining unexercised
shall be issued by the Rights Agent and delivered to, or upon the order of, the
registered holder of such Rights Certificate, registered in such name or names
as may be designated by such holder, subject to the provisions of Section 14
hereof.

                  (e) Notwithstanding anything in this Agreement to the
contrary, from and after the first occurrence of a Triggering Event, any Rights
beneficially owned by (i) an Acquiring Person or an Associate or Affiliate of an
Acquiring Person, (ii) a transferee of an Acquiring Person (or of any such
Associate or Affiliate) who becomes a transferee after the Acquiring Person
becomes such (a "Post Transferee"), or (iii) a transferee of an Acquiring Person
(or of any such Associate or Affiliate) who becomes a transferee prior to or
concurrently with the Acquiring Person becoming


                                       9
<PAGE>   13
such and receives such Rights pursuant to either (A) a transfer (whether or not
for consideration) from the Acquiring Person to holders of equity interests in
such Acquiring Person or to any Person with whom the Acquiring Person had any
continuing agreement, arrangement or understanding regarding the transferred
Rights or (B) a transfer which the Board of Directors of the Company has
determined is part of a plan, arrangement or understanding which has as a
primary purpose or effect the avoidance of this Section 7(e) (a "Prior
Transferee"), or (iv) any subsequent transferee receiving transferred Rights
from a Post Transferee or a Prior Transferee, either directly or through one or
more intermediate transferees, shall become null and void without any further
action and no holder of such Rights shall have any rights whatsoever with
respect to such Rights, whether under any provision of this Agreement or
otherwise. The Company shall use all reasonable efforts to insure that the
provisions of this Section 7(e) and Section 4(b) hereof are complied with, but
shall have no liability to any holder of Rights Certificates or other person as
a result of its failure to make any determinations with respect to an Acquiring
Person or its Affiliates, Associates or transferees hereunder.

                  (f) Notwithstanding anything in this Agreement to the
contrary, neither the Rights Agent nor the Company shall be obligated to
undertake any action with respect to a registered holder upon the occurrence of
any purported exercise as set forth in this Section 7 unless such registered
holder shall have (i) completed and signed the certificate contained in the form
of election to purchase set forth on the reverse side of the Rights Certificate
surrendered for such exercise, and (ii) provided such additional evidence of the
identity of the Beneficial Owner (or former Beneficial Owner) or Affiliates or
Associates thereof as the Company shall reasonably request.

         SECTION 8. CANCELLATION AND DESTRUCTION OF RIGHTS CERTIFICATES. All
Rights Certificates surrendered for the purpose of exercise, transfer, split up,
combination or exchange shall, if surrendered to the Company or any of its
agents, be delivered to the Rights Agent for cancellation or in cancelled form,
or, if surrendered to the Rights Agent, shall be cancelled by it, and no Rights
Certificates shall be issued in lieu thereof except as expressly permitted by
any of the provisions of this Agreement. The Company shall deliver to the Rights
Agent for cancellation and retirement, and the Rights Agent shall so cancel and
retire, any other Rights Certificate purchased or acquired by the Company
otherwise than upon the exercise thereof. The Rights Agent shall deliver all
cancelled Rights Certificates to the Company, or shall, at the written request
of the Company, destroy such cancelled Rights Certificates, and in such case
shall deliver a certificate of destruction thereof to the Company.

         SECTION 9. RESERVATION AND AVAILABILITY OF CAPITAL STOCK.

                  (a) The Company covenants and agrees that it will cause to be
reserved and kept available out of its authorized and unissued shares of
Preferred Stock (and, following the occurrence of a Triggering Event, out of its
authorized and unissued shares of Common Stock and/or other securities or out of
its authorized and issued shares held in its treasury), the number of shares of
Preferred Stock (and, following the occurrence of a Triggering Event, Common
Stock and/or other securities) that, as provided in this Agreement including
Section 11(a)(iii) hereof, will be sufficient to permit the exercise in full of
all outstanding Rights.

                  (b) So long as the shares of Preferred Stock (and following
the occurrence of a Triggering Event, Common Stock and/or other securities)
issuable and deliverable upon the exercise of the Rights may be listed on any
national securities exchange or the NASDAQ National Market


                                       10
<PAGE>   14
System (the "NMS"), the Company shall use its best efforts to cause, from and
after such time as the Rights become exercisable, all shares reserved for such
issuance to be listed on such exchange or the NMS upon official notice of
issuance upon such exercise.

                  (c) The Company shall use its best efforts to (i) file, as
soon as practicable following the earliest date after the first occurrence of a
Section 11(a)(ii) Event on which the consideration to be delivered by the
Company upon exercise of the Rights has been determined in accordance with
Section 11(a)(iii) hereof, or as soon as is required by law following the
Distribution Date, as the case may be, a registration statement under the
Securities Act of 1933 (the "Act"), with respect to the securities purchasable
upon exercise of the Rights on an appropriate form, (ii) cause such registration
statement to become effective as soon as practicable after such filing, and
(iii) cause such registration statement to remain effective (with a prospectus
at all times meeting the requirements of the Act) until the earlier of (A) the
date as of which the Rights are no longer exercisable for such securities, and
(B) the date of the expiration of the Rights. The Company will also take such
action as may be appropriate under, or to ensure compliance with, the securities
or "blue sky" laws of the various states in connection with the exercisability
of the Rights. The Company may temporarily suspend, for a period of time not to
exceed ninety (90) days after the date set forth in clause (i) of the first
sentence of this Section 9(c), the exercisability of the Rights in order to
prepare and file such registration statement and permit it to become effective.
Upon any such suspension, the Company shall issue a public announcement stating
that the exercisability of the Rights has been temporarily suspended, as well as
a public announcement at such time as the suspension is no longer in effect.
Notwithstanding any provision of this Agreement to the contrary, the Rights
shall not be exercisable in any jurisdiction unless the requisite qualification
in such jurisdiction shall have been obtained and until a registration statement
(if required) has been declared effective.

                  (d) The Company covenants and agrees that it will take all
such action as may be necessary to ensure that all one one-hundredths of a share
of Preferred Stock (and, following the occurrence of a Triggering Event, Common
Stock and/or other securities) delivered upon exercise of Rights shall, at the
time of delivery of the certificates for such shares (subject to payment of the
Purchase Price), be duly and validly authorized and issued and fully paid and
nonassessable.

                  (e) The Company further covenants and agrees that it will pay
when due and payable any and all federal and state transfer taxes and charges
which may be payable in respect of the issuance or delivery of the Rights
Certificates and of any certificates for shares of Preferred Stock (or Common
Stock and/or other securities,as the case may be) upon the exercise of Rights.
The Company shall not, however, be required to pay any transfer tax which may be
payable in respect of any transfer or delivery of Rights Certificates to a
Person other than, or the issuance or delivery of a number of one one-hundredths
of a share of Preferred Stock (or Common Stock and/or other securities, as the
case may be) in respect of a name other than that of, the registered holder of
the Rights Certificates evidencing Rights surrendered for exercise or to issue
or deliver any certificates for a number of one one-hundredths of a share of
Preferred Stock (or Common Stock and/or other securities, as the case may be) in
a name other than that of the registered holder upon the exercise of any Rights
until such tax shall have been paid (any such tax being payable by the holder of
such Rights Certificate at the time of surrender) or until it has been
established to the Company's satisfaction that no such tax is due.


                                       11
<PAGE>   15
         SECTION 10. PREFERRED STOCK RECORD DATE. Each person in whose name any
certificate for a number of one one-hundredths of a share of Preferred Stock (or
Common Stock and/or other securities, as the case may be) is issued upon the
exercise of Rights shall for all purposes be deemed to have become the holder of
record of such fractional shares of Preferred Stock (or Common Stock and/or
other securities, as the case may be) represented thereby on, and such
certificate shall be dated, the date upon which the Rights Certificate
evidencing such Rights was duly surrendered and payment of the Purchase Price
(and all applicable transfer taxes) was made; provided, however, that if the
date of such surrender and payment is a date upon which the Preferred Stock (or
Common Stock and/or other securities, as the case may be) transfer books of the
Company are closed, such Person shall be deemed to have become the record holder
of such shares (fractional or otherwise) on, and such certificate shall be
dated, the next succeeding Business Day on which the Preferred Stock (or Common
Stock and/or other securities,as the case may be) transfer books of the Company
are open. Prior to the exercise of the Rights evidenced thereby, the holder of a
Rights Certificate shall not be entitled to any rights of a stockholder of the
Company with respect to shares for which the Rights shall be exercisable,
including, without limitation, the right to vote, to receive dividends or other
distributions or to exercise any preemptive rights, and shall not be entitled to
receive any notice of any proceedings of the Company, except as provided herein.

         SECTION 11. ADJUSTMENT OF PURCHASE PRICE, NUMBER AND KIND OF SHARES OR
NUMBER OF RIGHTS. The Purchase Price, the number and kind of shares covered by
each Right and the number of Rights outstanding are subject to adjustment from
time to time as provided in this Section 11.

                  (a) (i) In the event the Company shall at any time after the
date of this Agreement (A) declare a dividend on the Preferred Stock payable in
shares of Preferred Stock, (B) subdivide the outstanding Preferred Stock, (C)
combine the outstanding Preferred Stock into a smaller number of shares, or (D)
issue any shares of its capital stock in a reclassification of the Preferred
Stock (including any such reclassification in connection with a consolidation or
merger in which the Company is the continuing or surviving corporation), except
as otherwise provided in this Section 11(a) and Section 7 hereof, the Purchase
Price in effect at the time of the record date for such dividend or of the
effective date of such subdivision, combination or reclassification, and the
number and kind of shares of Preferred Stock or capital stock, as the case may
be, issuable on such date, shall be proportionately adjusted so that the holder
of any Right exercised after such time shall be entitled to receive, upon
payment of the Purchase Price then in effect, the aggregate number and kind of
shares of Preferred Stock or capital stock, as the case may be, which, if such
Right had been exercised immediately prior to such date and at a time when the
Preferred Stock transfer books of the Company were open, he would have owned
upon such exercise and been entitled to receive by virtue of such dividend,
subdivision, combination or reclassification. If an event occurs which would
require an adjustment under both this Section 11(a)(i) and Section 11(a)(ii)
hereof, the adjustment provided for in this Section 11(a)(i) shall be in
addition to, and shall be made prior to, any adjustment required pursuant to
Section 11(a)(ii) hereof.

                           (ii)     In the event:

                                    (A) any Acquiring Person or any Associate or
         Affiliate of any Acquiring Person, at any time after the date of this
         Agreement, directly or indirectly, (1) shall merge into the Company or
         otherwise combine with the Company and the Company shall be the
         continuing or surviving corporation of such merger or combination and
         the


                                       12
<PAGE>   16
         Common Stock of the Company shall remain outstanding and unchanged, (2)
         shall, in one transaction or a series of transactions, transfer any
         assets to the Company or to any of its Subsidiaries in exchange (in
         whole or in part) for shares of Common Stock, for shares of other
         equity securities of the Company, or for securities exercisable for or
         convertible into shares of equity securities of the Company (Common
         Stock or otherwise) or otherwise obtain from the Company, with or
         without consideration, any additional shares of such equity securities
         or securities exercisable for or convertible into shares of such equity
         securities (other than pursuant to a pro rata distribution to all
         holders of Common Stock), (3) shall sell, purchase, lease, exchange,
         mortgage, pledge, transfer or otherwise acquire or dispose of, in the
         transaction or a series of transactions, to, from or with (as the case
         may be) the Company or any of its Subsidiaries, assets on terms and
         conditions less favorable to Company than the Company would be able to
         obtain in arm's length negotiation with an unaffiliated third party,
         other than pursuant to a transaction set forth in Section 13(a) hereof,
         (4) shall sell, purchase, lease, exchange, mortgage, pledge, transfer
         or otherwise acquire or dispose of in one transaction or a series of
         transactions, to, from or with (as the case may be) the Company or any
         of the Company's Subsidiaries (other than incidental to the lines of
         business, if any, engaged in as of the date hereof between the Company
         and such Acquiring Person or Associate or Affiliate) assets having an
         aggregate fair market value of more than $5,000,000, other than
         pursuant to a transaction set forth in Section 13(a) hereof, (5) shall
         receive any compensation from the Company or any of the Company's
         Subsidiaries other than compensation for full time employment as a
         regular employee at rates in accordance with the Company's (or its
         Subsidiaries') past practices, or (6) shall receive the benefit,
         directly or indirectly (except proportionately as a stockholder and
         except if resulting from a requirement of law or governmental
         regulation), of any loans, advances, guarantees, pledges or other
         financial assistance or any tax credits or other tax advantage provided
         by the Company or any of its Subsidiaries, or

                                    (B) any Person shall become an Acquiring
         Person, other than pursuant to any transaction set forth in Section 
         13(a) hereof, or

                                    (C) during such time as there is an
         Acquiring person, there shall be any reclassification of securities
         (including any reverse stock split), or recapitalization of the
         Company, or any merger or consolidation of the Company with any of its
         Subsidiaries or any other transaction or series of transactions
         involving the Company or any of its Subsidiaries, other than a
         transaction or transactions to which the provisions of Section 13(a)
         apply (whether or not with or into or otherwise involving an Acquiring
         Person) which has the effect, directly or indirectly, of increasing by
         more than 1% the proportionate share of the outstanding shares of any
         class of equity securities of the Company or any of its Subsidiaries
         which is directly or indirectly beneficially owned by any Acquiring
         Person or any Associate or Affiliate of any Acquiring Person,

         then, promptly following five (5) days after the date of the occurrence
         of an event described in Section 11(a)(ii)(B) hereof and promptly
         following the occurrence of any event described in Section 11(a)(ii)(A)
         or (C) hereof, proper provision shall be made so that each holder of a
         Right (except as provided below and in Section 7(e) hereof) shall
         thereafter have the right to receive, upon exercise thereof at the then
         current Purchase Price in accordance with the terms of this Agreement,
         in lieu of shares of Preferred Stock, such number of shares of Common
         Stock of the Company as shall equal the result obtained by (x)
         multiplying the then


                                       13
<PAGE>   17
         current Purchase Price by the then number of one one-hundredths of a
         share of Preferred Stock for which a Right was exercisable immediately
         prior to the first occurrence of a Section 11(a)(ii) Event, and
         dividing that product (which,following such first occurrence, shall
         thereafter be referred to as the "Purchase Price" for each Right and
         for all purposes of this Agreement) by (y) 50% of the current market
         price (determined pursuant to Section 11(d) hereof) per share of Common
         Stock on the date of such first occurrence (such number of shares, the
         "Adjustment Shares").

                           (iii) In the event that the number of shares of
Common Stock which are authorized by the Company's charter but not outstanding
or reserved for issuance for purposes other than upon exercise of the Rights are
not sufficient to permit the exercise in full of the Rights in accordance with
the foregoing subparagraph (ii) of this Section 11(a), the Company shall: (A)
determine the excess of (1) the value of the Adjustment Shares issuable upon the
exercise of a Right (the "Current Value") over (2) the Purchase Price (such
excess, the "Spread"), and (B) with respect to each Right, make adequate
provision to substitute for the Adjustment Shares, upon payment of the
applicable Purchase Price, (1) cash, (2) a reduction in the Purchase Price, (3)
Common Stock or other equity securities of the Company (including, without
limitation, shares, or units of shares, of preferred stock which the Board of
Directors of the Company has deemed to have the same value as shares of Common
Stock (such shares of preferred stock, "common stock equivalents")), (4) debt
securities of the Company, (5) other assets, or (6) any combination of the
foregoing, having an aggregate value equal to the Current Value, where such
aggregate value has been determined by the Board of Directors of the Company
based upon the advice of a nationally recognized investment banking firm
selected by the Board of Directors of the Company; provided, however, if the
Company shall not have made adequate provision to deliver value pursuant to
clause (B) above within thirty (30) days following the later of (x) the first
occurrence of a Section 11(a)(ii) Event and (y) the date on which the Company's
right of redemption pursuant to Section 23(a) expires (the later of (x) and (y)
being referred to herein as the "Section 11(a)(ii) Trigger Date"), then the
Company shall be obligated to deliver, upon the surrender for exercise of a
Right and without requiring payment of the Purchase Price, shares of Common
Stock (to the extent available) and then, if necessary, cash, which in the
aggregate are equal to the Spread. If the Board of Directors of the Company
shall determine in good faith that it is likely that sufficient additional
shares of Common Stock could be authorized for issuance upon exercise in full of
the Rights, the thirty (30) day period set forth above may be extended to the
extent necessary, but not more than ninety (90) days following the first
occurrence of a Section 11(a)(ii) Trigger Date, in order that the Company may
seek shareholder approval for the authorization of such additional shares (such
period, as it may be extended, the "Substitution Period"). To the extent that
the Company determines that some action need be taken pursuant to the first
and/or second sentences of this Section 11(a)(iii), the Company (x) shall
provide, subject to Section 7(e) hereof, that such action shall apply uniformly
to all outstanding Rights, and (y) may suspend the exercisability of the Rights
until the expiration of the Substitution Period in order to seek any
authorization of additional shares and/or to decide the appropriate form of
distribution to be made pursuant to such first sentence and to determine the
value thereof. In the event of any such suspension, the Company shall issue a
public announcement stating that the exercisability of the Rights has been
temporarily suspended, as well as a public announcement at such time as the
suspension is no longer in effect. For purposes of this Section 11(a)(iii), the
value of the Common Stock shall be the current market price (as determined
pursuant to Section 11(d) hereof) per share of the Common Stock on the date of
the first occurrence of a Section 11(a)(ii) Trigger Date and the value of any
"common stock equivalent" shall be deemed to have the same value as the Common
Stock on such date.


                                       14
<PAGE>   18
                           (iv) The right to buy Common Stock of the Company
pursuant to Section 11(a)(ii) hereof shall not arise as a result of any Person
becoming an Acquiring Person through an acquisition of Common Stock pursuant to
a Permitted Offer.

                  (b) In case the Company shall fix a record date for the
issuance of rights, options or warrants to all holders of Preferred Stock
entitling them to subscribe for or purchase (for a period expiring within
forty-five (45) calendar days after such record date) Preferred Stock (or shares
having the same rights, privileges and preferences as the shares of Preferred
Stock ("equivalent preferred stock")) or securities convertible into Preferred
Stock or equivalent preferred stock at a price per share of Preferred Stock or
per share of equivalent preferred stock (or having a conversion price per share,
if a security convertible into Preferred Stock or equivalent preferred stock)
less than the current market price (as determined pursuant to Section 11(d)
hereof) per share of Preferred Stock on such record date, the Purchase Price to
be in effect after such record date shall be determined by multiplying the
Purchase Price in effect immediately prior to such record date by a fraction,
the numerator of which shall be the number of shares of Preferred Stock
outstanding on such record date, plus the number of shares of Preferred Stock
which the aggregate offering price of the total number of shares of Preferred
Stock and/or equivalent preferred stock so to be offered (and/or the aggregate
initial conversion price of the convertible securities so to be offered) would
purchase at such current market price, and the denominator of which shall be the
number of shares of Preferred Stock outstanding on such record date, plus the
number of additional shares of Preferred Stock and/or equivalent preferred stock
to be offered for subscription or purchase (or into which the convertible
securities so to be offered are initially convertible); provided, however, that
in no event shall the consideration to be paid upon the exercise of one Right be
less than the aggregate par value of the shares of capital stock of the Company
issuable upon the exercise of one Right. In case such subscription price may be
paid by delivery of consideration part or all of which may be in a form other
than cash, the value of such consideration shall be as determined in good faith
by the Board of Directors of the Company, whose determination shall be described
in a statement filed with the Rights Agent and shall be binding on the Rights
Agent and the holders of the Rights. Shares of Preferred Stock owned by or held
for the account of the Company shall not be deemed outstanding for the purpose
of any such computation. Such adjustment shall be made successively whenever
such a record date is fixed, and in the event that such rights or warrants are
not so issued, the Purchase Price shall be adjusted to be the Purchase Price
which would then be in effect if such record date had not been fixed.

                  (c) In case the Company shall fix a record date for a
distribution to all holders of Preferred Stock (including any such distribution
made in connection with a consolidation or merger in which the Company is the
continuing corporation) of evidences of indebtedness, cash (other than a regular
quarterly cash dividend out of the earnings or retained earnings of the
Company), assets (other than a dividend payable in Preferred Stock, but
including any dividend payable in stock other than Preferred Stock) or
subscription rights or warrants (excluding those referred to in Section 11(b)
hereof), the Purchase Price to be in effect after such record date shall be
determined by multiplying the Purchase Price in effect immediately prior to such
record date by a fraction, the numerator of which shall be the current market
price (as determined pursuant to Section 11(d) hereof) per share of Preferred
Stock on such record date, less the fair market value (as determined in good
faith by the Board of Directors of the Company, whose determination shall be
described in a statement filed with the Rights Agent) of the portion of the
cash, assets or evidences of indebtedness so to be distributed or of such
subscription rights or warrants applicable to a share of Preferred Stock and the
denominator of which shall be such current market price (as


                                       15
<PAGE>   19
determined pursuant to Section 11(d) hereof) per share of Preferred Stock;
provided, however, that in no event shall the consideration to be paid upon the
exercise of one Right be less than the aggregate par value of the shares of
capital stock of the Company issuable upon the exercise of one Right. Such
adjustments shall be made successively whenever such a record date is fixed, and
in the event that such distribution is not so made, the Purchase Price shall be
adjusted to be the Purchase Price which would have been in effect if such record
date had not been fixed.

                  (d) (i) For the purpose of any computation hereunder, other
than computations made pursuant to Section 11(a)(iii) hereof, the "current
market price" per share of Common Stock on any date shall be deemed to be the
average of the daily closing prices per share of such Common Stock for the
thirty (30) consecutive Trading Days (as such term is hereinafter defined)
immediately prior to such date, and for purposes of computations made pursuant
to Section 11(a)(iii) hereof, the "current market price" per share of Common
Stock on any date shall be deemed to be the average of the daily closing prices
per share of such Common Stock for the ten (10) consecutive Trading Days
immediately following such date; provided, however, that in the event that the
current market price per share of the Common Stock is determined during a period
following the announcement by the issuer of such Common Stock of (A) a dividend
or distribution on such Common Stock payable in shares of such Common Stock or
securities convertible into shares of such Common Stock (other than the Rights),
or (B) any subdivision, combination or reclassification of such Common Stock,
and prior to the expiration of the requisite thirty (30) Trading Day or ten (10)
Trading Day period, as set forth above, after the dividend date for such
dividend or distribution, or the record date for such subdivision, combination
or reclassification, then, and in each such case, the "current market price"
shall be properly adjusted to take into account ex-dividend trading. The closing
price for each day shall be the last sale price, regular way, or, in case no
such sale takes place on such day, the average of the closing bid and asked
prices, regular way, in either case as reported in the principal consolidated
transaction reporting system with respect to securities listed or admitted to
trading on the New York Stock Exchange or, if the shares of Common Stock are not
listed or admitted to trading on the New York Stock Exchange, as reported in the
principal consolidated transaction reporting system with respect to securities
listed on the principal national securities exchange on which the shares of
Common Stock are listed or admitted to trading or, if the shares of Common Stock
are not listed or admitted to trading on any national securities exchange, the
last quoted price or, if not so quoted, the average of the high bid and low
asked prices in the over-the-counter market, as reported by the National
Association of Securities Dealers, Inc. Automated Quotation System ("NASDAQ") or
such other system then in use, or, if on any such date the shares of Common
Stock are not quoted by any such organization, the average of the closing bid
and asked prices as furnished by a professional market maker making a market in
the Common Stock selected by the Board of Directors of the Company. If on any
such date no market maker is making a market in the Common Stock, the fair value
of such shares on such date as determined in good faith by the Board of
Directors of the Company shall be used. The term "Trading Day" shall mean a day
on which the principal national securities exchange on which the shares of
Common Stock are listed or admitted to trading is open for the transaction of
business or, if the shares of Common Stock are not listed or admitted to trading
on any national securities exchange, a Business Day. If the Common Stock is not
publicly held or not so listed or traded, "current market price" per share shall
mean the fair value per share as determined in good faith by the Board of
Directors of the Company, whose determination shall be described in a statement
filed with the Rights Agent and shall be conclusive for all purposes.


                                       16
<PAGE>   20
                           (ii) For the purpose of any computation hereunder,
the "current market price" per share of Preferred Stock shall be determined in
the same manner as set forth above for the Common Stock in clause (i) of this
Section 11(d) (other than the last sentence thereof). If the current market
price per share of Preferred Stock cannot be determined in the manner provided
above or if the Preferred Stock is not publicly held or listed or traded in a
manner described in clause (i) of this Section 11(d), the "current market price"
per share of Preferred Stock shall be conclusively deemed to be an amount equal
to 100 (as such number may be appropriately adjusted for such events as stock
splits, stock dividends and recapitalizations with respect to the Common Stock
occurring after the date of this Agreement) multiplied by the current market
price per share of the Common Stock. If neither the Common Stock nor the
Preferred Stock is publicly held or so listed or traded, "current market price"
per share of the Preferred Stock shall mean the fair value per share as
determined in good faith by the Board of Directors of the Company, whose
determination shall be described in a statement filed with the Rights Agent and
shall be conclusive for all purposes. For all purposes of this Agreement, the
"current market price" of one one-hundredth of a share of Preferred Stock shall
be equal to the "current market price" of one share of Preferred Stock divided
by 100.

                  (e) Anything herein to the contrary notwithstanding, no
adjustment in the Purchase Price shall be required unless such adjustment would
require an increase or decrease of at least one percent (1%) in the Purchase
Price; provided, however, that any adjustments which by reason of this Section 
11(e) are not required to be made shall be carried forward and taken into
account in any subsequent adjustment. All calculations under this Section 11
shall be made to the nearest cent or to the nearest ten-thousandth of a share of
Common Stock or other share or one-millionth of a share of Preferred Stock, as
the case may be. Notwithstanding the first sentence of this Section 11(e), any
adjustment required by this Section 11 shall be made no later than the earlier
of (i) three (3) years from the date of the transaction which mandates such
adjustment, or (ii) the Expiration Date.

                  (f) If as a result of an adjustment made pursuant to Section 
11(a)(ii) or Section 13(a) hereof, the holder of any Right thereafter exercised
shall become entitled to receive any shares of capital stock other than
Preferred Stock, thereafter the number of such other shares so receivable upon
exercise of any Right and the Purchase Price thereof shall be subject to
adjustment from time to time in a manner and on terms as nearly equivalent as
practicable to the provisions with respect to the Preferred Stock contained in
Sections 11(a), (b), (c), (e), (g), (h), (i), (j), (k) and (m), and the
provisions of Sections 7, 9, 10, 13 and 14 hereof with respect to the Preferred
Stock shall apply on like terms to any such other shares.

                  (g) All Rights originally issued by the Company subsequent to
any adjustment made to the Purchase Price hereunder shall evidence the right to
purchase, at the adjusted Purchase Price, the number of one one-hundredths of a
share of Preferred Stock purchasable from time to time hereunder upon exercise
of the Rights, all subject to further adjustment as provided herein.

                  (h) Unless the Company shall have exercised its election as
provided in Section 11(i), upon each adjustment of the Purchase Price as a
result of the calculations made in Sections 11(b) and (c), each Right
outstanding immediately prior to the making of such adjustment shall thereafter
evidence the right to purchase, at the adjusted Purchase Price, that number of
one one-hundredths of a share of Preferred Stock (calculated to the nearest
one-millionth) obtained by (i) multiplying (x) the number of one one-hundredths
of a share covered by a Right immediately price to this adjustment, by (y) the
Purchase Price in effect immediately prior to such adjustment of


                                       17
<PAGE>   21
the Purchase Price, and (ii) dividing the product so obtained by the Purchase
Price in effect immediately after such adjustment of the Purchase Price.

                  (i) The Company may elect on or after the date of any
adjustment of the Purchase Price to adjust the number of Rights, in lieu of any
adjustment in the number of one one-hundredths of a share of Preferred Stock
purchasable upon the exercise of a Right. Each of the Rights outstanding after
the adjustment in the number of Rights shall be exercisable for the number of
one one-hundredths of a share of Preferred Stock for which a Right was
exercisable immediately prior to such adjustment. Each Right held of record
prior to such adjustment of the number of Rights shall become that number of
Rights (calculated to the nearest one-ten-thousandth) obtained by dividing the
Purchase Price in effect immediately prior to adjustment of the Purchase Price
by the Purchase Price in effect immediately after adjustment of the Purchase
Price. The Company shall make a public announcement of its election to adjust
the number of Rights, indicating the record date for the adjustment, and, if
known at the time, the amount of the adjustment to be made. This record date may
be the date on which the Purchase Price is adjusted or any day thereafter, but,
if the Rights Certificates have been issued, shall be at least ten (10) days
later than the date of the public announcement. If Rights Certificates have been
issued, upon each adjustment of the number of Rights pursuant to this Section 
11(i), the Company shall, as promptly as practicable, cause to be distributed to
holders of record of Rights Certificates on such record date Rights Certificates
evidencing, subject to Section 14 hereof, the additional Rights to which such
holders shall be entitled as a result of such adjustment, or, at the option of
the Company, shall cause to be distributed to such holders of record in
substitution and replacement for the Rights Certificates held by such holders
prior to the date of adjustment, and upon surrender thereof, if required by the
Company, new Rights Certificates evidencing all the Rights to which such holders
shall be entitled after such adjustment. Rights Certificates so to be
distributed shall be issued, executed and countersigned in the manner provided
for herein (and may bear, at the option of the Company, the adjusted Purchase
Price) and shall be registered in the names of the holders of record of Rights
Certificates on the record date specified in the public announcement.

                  (j) Irrespective of any adjustment or change in the Purchase
Price or the number of one one-hundredths of a share of Preferred Stock issuable
upon the exercise of the Rights, the Rights Certificates theretofore and
thereafter issued may continue to express the Purchase Price per one
one-hundredth of a share and the number of one one-hundredth of a share which
were expressed in the initial Rights Certificates issued hereunder.

                  (k) Before taking any action that would cause an adjustment
reducing the Purchase Price below the then par or stated value, if any, of the
number of one one-hundredths of a share of Preferred Stock issuable upon
exercise of the Rights, the Company shall take any corporate action which may,
in the opinion of its counsel, be necessary in order that the Company may
validly and legally issue fully paid and nonassessable such number of one
one-hundredths of a share of Preferred Stock at such adjusted Purchase Price.

                  (l) In any case in which this Section 11 shall require that an
adjustment in the Purchase Price be made effective as of a record date for a
specified event, the Company may elect to defer until the occurrence of such
event the issuance to the holder of any Right exercised after such record date
the number of one one-hundredths of a share of Preferred Stock and other capital
stock or securities of the Company, if any, issuable upon such exercise over and
above the number of one one-hundredths of a share of Preferred Stock and other
capital stock or securities of the


                                       18
<PAGE>   22
Company, if any, issuable upon such exercise on the basis of the Purchase Price
in effect prior to such adjustment; provided, however, that the Company shall
deliver to such holder a due bill or other appropriate instrument evidencing
such holder's right to receive such additional shares (fractional or otherwise)
or securities upon the occurrence of the event requiring such adjustment.

                  (m) Anything in this Section 11 to the contrary
notwithstanding, the Company shall be entitled to make such reductions in the
Purchase Price, in addition to those adjustments expressly required by this
Section 11, as and to the extent that in their good faith judgment the Board of
Directors of the Company shall determine to be advisable in order that any (i)
consolidation or subdivision of the Preferred Stock, (ii) issuance wholly for
cash of any shares of Preferred Stock at less than the current market price,
(iii) issuance wholly for cash of shares of Preferred Stock or securities which
by their terms are convertible into or exchangeable for shares of Preferred
Stock, (iv) stock dividend or (v) issuance of rights, options or warrants
referred to in this Section 11, hereafter made by the Company to holders of its
Preferred Stock shall not be taxable to such stockholders.

                  (n) The Company covenants and agrees that it shall not, at any
time after the Distribution Date, (i) consolidate with any other Person (other
than a Subsidiary of the Company in a transaction which complies with Section 
11(o) hereof), (ii) merge with or into any other Person (other than a Subsidiary
of the Company in a transaction which complies with Section 11(o) hereof), or
(iii) sell or transfer (or permit any Subsidiary to sell or transfer), in one
transaction, or a series of related transactions, assets or earning power
aggregating more than 50% of the assets or earning power of the Company and its
Subsidiaries (taken as a whole) to any other Person or Persons (other than the
Company and or any of its Subsidiaries in one or more transactions each of which
complies with Section 11(o) hereof), if (x) at the time of or immediately after
such consolidation, merger or sale there are any rights, warrants or other
instruments or securities outstanding or agreements in effect which would
substantially diminish or otherwise eliminate the benefits intended to be
afforded by the Rights or (y) prior to, simultaneously with or immediately after
such consolidation, merger or sale, the shareholders of the Person who
constitutes, or would constitute, the "Principal Party" for the purposes of
Section 13(a) hereof shall have received a distribution of Rights previously
owned by such Person or any of its Affiliates and Associates.

                  (o) The Company covenants and agrees that, after the
Distribution Date, it will not, except as permitted by Section 23, Section 24 or
Section 27 hereof, take (or permit any Subsidiary to take) any action if at the
time such action is taken it is reasonably foreseeable that such action will
diminish substantially or otherwise eliminate the benefits intended to be
afforded by the Rights.

                  (p) Anything in this Agreement to the contrary
notwithstanding, in the event that the Company shall at any time after the
Rights Dividend Declaration Date and prior to the Distribution Date (i) declare
a dividend on the outstanding shares of Common Stock payable in shares of Common
Stock, (ii) subdivide the outstanding Common Stock, or (iii) combine the
outstanding Common Stock into a smaller number of shares, the number of Rights
associated with each share of Common Stock then outstanding, or issued or
delivered thereafter but prior to the Distribution Date, shall be
proportionately adjusted so that the number of Rights thereafter associated with
each share of Common Stock following any such event shall equal the result
obtained by multiplying the number of Rights associated with each share of
Common Stock immediately prior to such event by a fraction the numerator which
shall be the total number of shares of Common


                                       19
<PAGE>   23
Stock outstanding immediately prior to the occurrence of the event and the
denominator of which shall be the total number of shares of Common Stock
outstanding immediately following the occurrence of such event.

         SECTION 12. CERTIFICATE OF ADJUSTED PURCHASE PRICE OR NUMBER OF SHARES.
Whenever an adjustment is made as provided in Section 11 and Section 13 hereof,
the Company shall (a) promptly prepare a certificate setting forth such
adjustment and a brief statement of the facts accounting for such adjustment,
(b) promptly file with the Rights Agent, and with each transfer agent for the
Preferred Stock and the Common Stock, a copy of such certificate, and (c) mail a
brief summary thereof to each holder of a Rights Certificate (or, if prior to
the Distribution Date, to each holder of a certificate representing shares of
Common Stock) in accordance With Section 26 hereof. Notwithstanding the
foregoing sentence, the failure of the Company to make such certification or
give such notice shall not affect the validity of such adjustment or the force
or effect of the requirement for such adjustment. The Rights Agent shall be
fully protected in relying on any such certificate and on any adjustment therein
contained.

         SECTION 13. CONSOLIDATION, MERGER OR SALE OR TRANSFER OF ASSETS OR
EARNING POWER.

                  (a) In the event that, following the Stock Acquisition Date,
directly or indirectly, (x) the Company shall consolidate with, or merge with
and into, any other Person (other than a Subsidiary of the Company in a
transaction which complies with Section 11(o) hereof), and the Company shall not
be the continuing or surviving corporation of such consolidation or merger, (y)
any Person (other than a Subsidiary of the Company in a transaction which
complies with Section 11(o) hereof) shall consolidate with, or merge with or
into, the Company, and the Company shall be the continuing or surviving
corporation of such consolidation or merger and, in connection with such
consolidation or merger, all or part of the outstanding shares of Common Stock
shall be changed into or exchanged for stock or other securities of any other
Person or cash or any other property, or (z) the Company shall sell or otherwise
transfer (or one or more of its Subsidiaries shall sell or otherwise transfer),
in one transaction or a series of related transactions, assets or earning power
aggregating more than 50% of the assets or earning power of the Company and its
Subsidiaries (taken as a whole) to any Person or Persons (other than the Company
or any Subsidiary of the Company in one or more transactions each of which
complies with Section 11(o) hereof), then, and in each such case, proper
provision shall be made so that: (i) each holder of a Right, except as provided
in Section 7(e) hereof, shall thereafter have the right to receive, upon the
exercise thereof at the then current Purchase Price in accordance with the terms
of this Agreement, such number of validly authorized and issued, fully paid,
non-assessable and freely tradeable shares of Common Stock of the Principal
Party (as such term is hereinafter defined), not subject to any liens,
encumbrances, rights of first refusal or other adverse claims, as shall be equal
to the result obtained by (1) multiplying the then current Purchase Price by the
number of one one-hundredths of a share of Preferred Stock for which a Right is
exercisable immediately prior to the first occurrence of a Section 13 Event (or,
if a Section 11(a)(ii) Event has occurred prior to the first occurrence of a
Section 13 Event, multiplying the number of such one one-hundredths of a share
for which a Right was exercisable immediately prior to the first occurrence of a
Section 11(a)(ii) Event by the Purchase Price in effect immediately prior to
such first occurrence), and (2) dividing that product (which, following the
first occurrence of a Section 13 Event, shall be referred to as the "Purchase
Price" for each Right and for all purposes of this Agreement) by 50% of the
current market price (determined pursuant to Section 11(d)(i) hereof) per share
of the Common Stock of such Principal Party on the date of consummation of such
Section 13 Event; (ii) such Principal Party shall thereafter be liable


                                       20
<PAGE>   24
for, and shall assume, by virtue of such Section 13 Event, all the obligations
and duties of the Company pursuant to this Agreement; (iii) the term "Company"
shall thereafter be deemed to refer to such Principal Party, it being
specifically intended that the provisions of Section 11 hereof shall apply only
to such Principal Party following the first occurrence of a Section 13 Event;
(iv) such Principal Party shall take such steps (including, but not limited to,
the reservation of a sufficient number of shares of its Common Stock) in
connection with the consummation of any such transaction as may be necessary to
assure that the provisions hereof shall thereafter be applicable, as nearly as
reasonably may be, in relation to its shares of Common Stock thereafter
deliverable upon the exercise of the Rights; provided, however, that upon the
subsequent occurrence of any merger, consolidation, sale of all or substantially
all assets, recapitalization, reclassification of shares, reorganization or
other extraordinary transaction in respect of such Principal Party, each holder
of a Right shall thereupon be entitled to receive, upon exercise of a Right a
payment of the Purchase Price, such cash, shares, rights, warrants and other
property which such holder would have been entitled to receive had he, at the
time of such transaction, owned the shares of Common Stock of the Principal
Party purchasable upon the exercise of a Right, and such Principal Party shall
take such steps (including, but not limited to, reservation of shares of stock)
as may be necessary to permit the subsequent exercise of the Rights in
accordance with the terms hereof for such cash, shares, rights, warrants and
other property; and (v) the provisions of Section 11(a)(ii) hereof shall be of
no effect following the first occurrence of any Section 13 Event.

                  (b)      "Principal Party" shall mean:

                           (i) in the case of any transaction described in
         clause (x) or (y) of the first sentence of Section 13(a), the Person
         that is the issuer of any securities into which shares of Common Stock
         of the Company are converted in such merger or consolidation, and if no
         securities are so issued, the Person that is the other party to such
         merger or consolidation; and

                           (ii) in the case of any transaction described in
         clause (z) of the first sentence of Section 13(a), the Person that is
         the party receiving the greatest portion of the assets or earning power
         transferred pursuant to such transaction or transactions;

provided, however, that in any such case, (1) if the Common Stock of such Person
is not at such time and has not been continuously over the preceding twelve (12)
month period registered under Section 12 of the Exchange Act, and such Person is
a direct or indirect Subsidiary of another Person the Common Stock of which is
and has been so registered, "Principal Party" shall refer to such other Person;
and (2) in case such Person is a Subsidiary, directly or indirectly, of more
than one Person, the Common Stocks of two or more of which are and have been so
registered, "Principal Party" shall refer to whichever of such Persons is the
issuer of the Common Stock having the greatest aggregate market value.

                  (c) If, for any reason, the Rights cannot be exercised for
Common Stock of such Principal Party as provided in Section 13(a), then each
holder of Rights shall have the right to exchange its Rights for cash from such
Principal Party in an amount equal to the number of shares of Common Stock that
it would otherwise be entitled to purchase times 50% of the current per share
market price, as determined pursuant to Section 11(d) hereof, of such Common
Stock of such Principal Party. If, for any reason, the foregoing formulation
cannot be applied to determine the cash amount into which the Rights are
exchangeable, then the Board of Directors, based upon the


                                       21
<PAGE>   25
advice of one or more nationally recognized investment banking firms, and based
upon the total value of the Company, shall determine such amount reasonably and
with good faith to the holders of Rights. Any such determination shall be final
and binding on the Rights Agent.

                  (d) Notwithstanding anything in this Agreement to the
contrary, Section 13 shall not be applicable to a transaction described in
clauses (x) and (y) of Section 13(a) if: (i) such transaction is consummated
with a Person or Persons who acquired Common Stock pursuant to a Permitted Offer
(or a wholly-owned Subsidiary of any such Person or Persons); (ii) the price per
share of Common Stock offered in such transaction is not less than the price per
share of Common Stock paid to all holders of Common Stock whose shares were
purchased pursuant to such Permitted Offer; and (iii) the form of consideration
being offered to the remaining holders of Common Stock pursuant to such
transaction is the same form as the form of consideration paid pursuant to such
Permitted Offer. Upon consummation of any such transaction contemplated by this
Section 13(d), all Rights hereunder shall expire.

                  (e) The Company shall not consummate any such consolidation,
merger, sale or transfer unless the Principal Party shall have a sufficient
number of authorized shares of its Common Stock which have not been issued or
reserved for issuance to permit the exercise in full of the Rights in accordance
with this Section 13 and unless prior thereto the Company and such Principal
Party shall have executed and delivered to the Rights Agent a supplemental
agreement providing for the terms set forth in paragraphs (a) and (b) of this
Section 13 and further providing that, as soon as practicable after the date of
any consolidation, merger or sale of assets mentioned in paragraph (a) of this
Section 13, the principal Party will:

                           (i) prepare and file a registration statement under
         the Act, with respect to the Rights and the securities purchasable upon
         exercise of the Rights on an appropriate form, and will use its best
         efforts to cause such registration statement to (A) become effective as
         soon as practicable after such filing and (B) remain effective (with a
         prospectus at all times meeting the requirements of the Act) until the
         Expiration Date;

                           (ii) deliver to holders of the Rights historical
         financial statements for the Principal Party and each of its Affiliates
         which comply in all respects with the requirements for registration on
         Form 10 under the Exchange Act;

                           (iii) use its best efforts, if the Common Stock of
         the Principal Party shall become listed on a national securities
         exchange, to list (or continue the listing of) the Rights and the
         securities purchasable upon exercise of the Rights on such securities
         exchange and, if the Common Stock of the Principal Party shall not be
         listed on a national securities exchange, to cause the Rights and the
         securities purchasable upon exercise of the Rights to be reported by
         NASDAQ or such other system then in use; and

                           (iv) obtain waivers of any rights of first refusal or
         preemptive rights in respect of the shares of Common Stock of the
         Principal Party subject to purchase upon exercise of outstanding
         Rights.

                  (f) The provisions of this Section 13 shall similarly apply to
successive mergers or consolidations or sales or other transfers. In the event
that a Section 13 Event shall occur at any


                                       22
<PAGE>   26
time after the occurrence of a Section 11(a)(ii) Event, the Rights which have
not theretofore been exercised shall thereafter become exercisable in the manner
described in Section 13(a).

      SECTION 14. FRACTIONAL RIGHTS AND FRACTIONAL SHARES.

            (a) The Company shall not be required to issue fractions of Rights,
except prior to the Distribution Date as provided in Section 11(p) hereof, or to
distribute Rights Certificates which evidence fractional Rights. In lieu of such
fractional Rights, there shall be paid to the registered holders of the Rights
Certificates with regard to which such fractional Rights would otherwise be
issuable, an amount in cash equal to the same fraction of the current market
value of a whole Right. For purposes of this Section 14(a), the current market
value of a whole Right shall be the closing price of the Rights for the Trading
Day immediately prior to date on which such fractional Rights would have been
otherwise issuable. The closing price of the Rights for any day shall be the
last sale price, regular way, or, in case no such sale takes place on such day,
the average of the closing bid and asked prices, regular way, in either case as
reported in the principal consolidated transaction reporting system with respect
to securities listed or admitted to trading on the New York Stock Exchange or,
if the Rights are not listed or admitted to trading on the New York Stock
Exchange, as reported in the principal consolidated transaction reporting system
with respect to securities listed on the principal national securities exchange
on which the Rights are listed or admitted to trading, or if the Rights are not
listed or admitted to trading on any national securities exchange, the last
quoted price or, if not so quoted, the average of the high bid and low asked
prices in the over-the-counter market, as reported by NASDAQ or such other
system then in use or, if on any such date the Rights are not quoted by any such
organization, the average of the closing bid and asked prices as furnished by a
professional market maker making a market in the Rights selected by the Board of
Directors of the Company. If on any such date no such market maker is making a
market in the Rights the fair value of the Rights on such date as determined in
good faith by the Board of Directors of the Company shall be used.

            (b) The Company shall not be required to issue fractions of shares
of Preferred Stock (other than fractions which are integral multiples of one
one-hundredth of a share of Preferred Stock) upon exercise of the Rights or to
distribute certificates which evidence fractional shares of Preferred Stock
(other than fractions which are integral multiples of one one-hundredth of a
share of Preferred Stock). In lieu of fractional shares of Preferred Stock that
are not integral multiples of one one-hundredth of a share of Preferred Stock,
the Company may pay to the registered holders of Rights Certificates at the time
such Rights are exercised as herein provided an amount in cash equal to the same
fraction of the current market value of one one-hundredth of a share of
Preferred Stock. For purposes of this Section 14(b), the current market value of
one one-hundredth of a share of Preferred Stock shall be one one-hundredth of
the closing price of a share of Preferred Stock (as determined pursuant to
Section 11(d)(ii) hereof) for the Trading Day immediately prior to the date of
such exercise.

            (c) Following the occurrence of a Triggering Event, the Company
shall not be required to issue fractions of shares of Common Stock upon exercise
of the Rights or to distribute certificates which evidence fractional shares of
Common Stock. In lieu of fractional shares of Common Stock, the Company may pay
to the registered holders of Rights Certificates at the time such Rights are
exercised as herein provided an amount in cash equal to the same fraction of the
current market value of one (1) share of Common Stock. For purposes of this
Section 14(c), the current market value of one share of Common Stock shall be
the closing price of one share of


                                       23
<PAGE>   27
Common Stock (as determined pursuant to Section 11(d)(i) hereof) for the Trading
Day immediately prior to the date of such exercise.

            (d) The holder of a Right by the acceptance of the Rights expressly
waives his right to receive any fractional Rights or any fractional shares upon
exercise of a Right, except as permitted by this Section 14.

      SECTION 15. RIGHTS OF ACTION. All rights of action in respect of this
Agreement are vested in the respective registered holders of the Rights
Certificates (and, prior to the Distribution Date, the registered holders of the
Common Stock); and any registered holder of any Rights Certificate (or, prior to
the Distribution Date, of the Common Stock), without the consent of the Rights
Agent or of the holder of any other Rights Certificate (or, prior to the
Distribution Date, of the Common Stock), may, in his own behalf and for his own
benefit, enforce, and may institute and maintain any suit, action or proceeding
against the Company to enforce, or otherwise act in respect of, his right to
exercise the Rights evidenced by such Rights Certificate in the manner provided
in such Rights Certificate and in this Agreement. Without limiting the foregoing
or any remedies available to the holders of Rights, it is specifically
acknowledged that the holders of Rights would not have an adequate remedy at law
for any breach of this Agreement and shall be entitled to specific performance
of the obligations hereunder and injunctive relief against actual or threatened
violations of the obligations hereunder of any Person subject to this Agreement.

      SECTION 16. AGREEMENT OF RIGHTS HOLDERS. Every holder of a Right by
accepting the same consents and agrees with the Company and the Rights Agent and
with every other holder of a Right that:

            (a) prior to the Distribution Date, the Rights will be transferable
only in connection with the transfer of Common Stock;

            (b) after the Distribution Date, the Rights Certificates are
transferable only on the registry books of the Rights Agent if surrendered at
the principal office or offices of the Rights Agent designated for such
purposes, duly endorsed or accompanied by proper instrument of transfer and with
the appropriate forms and certificates fully executed;

            (c) subject to Section 6(a) and Section 7(f) hereof, the Company and
the Rights Agent may deem and treat the person in whose name a Rights
Certificate (or, prior to the Distribution Date, the associated Common Stock
certificate) is registered as the absolute owner thereof and of the Rights
evidenced thereby (notwithstanding any notations of ownership or writing on the
Rights Certificates or the associated Common Stock certificate made by anyone
other than the Company or the Rights Agent) for all purposes whatsoever, and
neither the Company nor the Rights Agent shall be required to be affected by any
notice to the contrary; and

            (d) notwithstanding anything in this Agreement to the contrary,
neither the Company nor the Rights Agent shall have any liability to any holder
of a Right or other Person as a result of its inability to perform any of its
obligations under this Agreement by reason of any preliminary or permanent
injunction or other order, decree or ruling issued by a court of competent
jurisdiction or by a governmental, regulatory or administrative agency or
commission, or any statute, rule, regulation or executive order promulgated or
enacted by any governmental authority, prohibiting or otherwise restraining
performance of such obligation; provided, however, the


                                       24
<PAGE>   28
Company must use its best efforts to have any such order, decree or ruling
lifted or otherwise overturned as soon as possible.

      SECTION 17. RIGHTS CERTIFICATE HOLDER NOT DEEMED A STOCKHOLDER. No holder,
as such, of any Rights Certificate shall be entitled to vote, receive dividends
or be deemed for any purpose the holder of the number of one one-hundredths of a
share of Preferred Stock or any other securities of the Company which may at any
time be issuable on the exercise of the Rights represented thereby, nor shall
anything contained herein or in any Rights Certificate be construed to confer
upon the holder of any Rights Certificate, as such, any of the rights of a
stockholder of the Company or any right to vote for the election of directors or
upon any matter submitted to stockholders at any meeting thereof, or to give or
withhold consent to any corporate action, or to receive notice of meetings or
other actions affecting stockholders (except as provided in Section 25 hereof),
or to receive dividends or subscription rights, or otherwise, until the Right or
Rights evidenced by such Rights Certificate shall have been exercised in
accordance with the provisions hereof.

      SECTION 18. CONCERNING THE RIGHTS AGENT.

            (a) The Company agrees to pay to the Rights Agent reasonable
compensation for all services rendered by it hereunder and, from time to time,
on demand of the Rights Agent, its reasonable expenses and counsel fees and
disbursements and other disbursements incurred in the administration and
execution of this Agreement and the exercise and performance of its duties
hereunder. The Company also agrees to indemnify the Rights Agent for, and to
hold it harmless against, any loss, liability, or expense, incurred without
negligence, bad faith or willful misconduct on the part of the Rights Agent, of
anything done or omitted by the Rights Agent in connection with the acceptance
and administration of this Agreement, including the costs and expenses of
defending against any claim of liability in the premises.

            (b) The Rights Agent shall be protected and shall incur no liability
for or in respect of any action taken, suffered or omitted by it in connection
with its administration of this Agreement in reliance upon any Rights
Certificate or certificate for Common Stock or for other securities of the
Company, instrument of assignment or transfer, power of attorney, endorsement,
affidavit, letter, notice, direction, consent, certificate, statement, or other
paper or document believed by it to be genuine and to be signed, executed and,
where necessary, verified or acknowledged, by the proper Person or Persons, or
otherwise upon the advice of counsel as set forth in Section 20 hereof.

      SECTION 19. MERGER OR CONSOLIDATION OR CHANGE OF NAME OF RIGHTS AGENT.

            (a) Any corporation into which the Rights Agent or any successor
Rights Agent may be merged or with which it may be consolidated, or any
corporation resulting from any merger or consolidation to which the Rights Agent
or any successor Rights Agent shall be a party, or any corporation succeeding to
the stock transfer or corporate trust business of the Rights Agent or any
successor Rights Agent, shall be the successor to the Rights Agent under this
Agreement without the execution or filing of any paper or any further act on the
part of any of the parties hereto; provided, however, that such corporation
would be eligible for appointment as a successor Rights Agent under the
provisions of Section 21 hereof. In case at the time such successor Rights Agent
shall succeed to the agency created by this Agreement, any of the Rights
Certificates shall have been countersigned but not delivered, any such successor
Rights Agent may adopt the countersignature of a predecessor


                                       25
<PAGE>   29
Rights Agent and deliver such Rights Certificates so countersigned; and in case
at that time any of the Rights Certificates shall not have been countersigned,
any successor Rights Agent may countersign such Rights Certificates either in
the name of the predecessor or in the name of the successor Rights Agent; and in
all such cases such Rights Certificates shall have the full force provided in
the Rights Certificates and in this Agreement.

            (b) In case at any time the name of the Rights Agent shall be
changed and at such time any of the Rights Certificates shall have been
countersigned but not delivered, the Rights Agent may adopt the countersignature
under its prior name and deliver Rights Certificates so countersigned; and in
case at that time any of the Rights Certificates shall not have been
countersigned, the Rights Agent may countersign such Rights Certificates either
in its prior name or in its changed name; and in all such cases such Rights
Certificates shall have the full force provided in the Rights Certificates and
in this Agreement.

      SECTION 20. DUTIES OF RIGHTS AGENT. The Rights Agent undertakes the duties
and obligations imposed by this Agreement upon the following terms and
conditions, by all of which the Company and the holders of Rights Certificates,
by their acceptance thereof, shall be bound:

            (a) The Rights Agent may consult with legal counsel (who may be
legal counsel for the Company), and the opinion of such counsel shall be full
and complete authorization and protection to the Rights Agent as to any action
taken or omitted by it in good faith and in accordance with such opinion.

            (b) Whenever in the performance of its duties under this Agreement
the Rights Agent shall deem it necessary or desirable that any fact or matter
(including, without limitation, the identity of any Acquiring Person and the
determination of "current market price") be proved or established by the Company
prior to taking or suffering any action hereunder such fact or matter (unless
other evidence in respect thereof be herein specifically prescribed) may be
deemed to be conclusively proved and established by a certificate signed by the
Chairman of the Board, the President, any Vice President, the Treasurer, any
Assistant Treasurer, the Secretary or any Assistant Secretary of the Company and
delivered to the Rights Agent; and such certificate shall be full authorization
to the Rights Agent for any action taken or suffered in good faith by it under
the provisions of this Agreement in reliance upon such certificate.

            (c) The Rights Agent shall be liable hereunder only for its own
negligence, bad faith or willful misconduct.

            (d) The Rights Agent shall not be liable for or by reason of any of
the statements of fact or recitals contained in this Agreement or in the Rights
Certificates or be required to verify the same (except as to its
countersignature on such Rights Certificates), but all such statements and
recitals are and shall be deemed to have been made by the Company only.

            (e) The Rights Agent shall not be under any responsibility in
respect of the validity of this Agreement or the execution and delivery hereof
(except the due execution hereof by the Rights Agent) or in respect of the
validity or execution of any Rights Certificate (except its countersignature
thereof); nor shall it be responsible for any breach by the Company of any
covenant or condition contained in this Agreement or in any Rights Certificate;
nor shall it be responsible for any adjustment required under the provisions of
Section 11 or Section 13 hereof or responsible for


                                       26
<PAGE>   30
the manner, method or amount of any such adjustment or the ascertaining of the
existence of facts that would require any such adjustment (except with respect
to the exercise of Rights evidenced by Rights Certificates after actual notice
of any such adjustment); nor shall it by any act hereunder be deemed to make any
representation or warranty as to the authorization or reservation of any shares
of Common Stock or Preferred Stock to be issued pursuant to this Agreement or
any Rights Certificate or as to whether any shares of Common Stock or Preferred
Stock will, when so issued, be validly authorized and issued, fully paid and
nonassessable.

            (f) The Company agrees that it will perform, execute, acknowledge
and deliver or cause to be performed, executed, acknowledged and delivered all
such further and other acts, instruments and assurances as may reasonably be
required by the Rights Agent for the carrying out or performing by the Rights
Agent of the provisions of this Agreement.

            (g) The Rights Agent is hereby authorized and directed to accept
instructions with respect to the performance of its duties hereunder from the
Chairman of the Board, the President, any Vice President, the Secretary, any
Assistant Secretary, the Treasurer or any Assistant Treasurer of the Company,
and to apply to such officers for advice or instructions in connection with its
duties, and it shall not be liable for any action taken or suffered to be taken
by it in good faith in accordance with instructions of any such officer or for
any delay in acting while waiting for those instructions.

            (h) The Rights Agent and any stockholder, director, officer or
employee of the Rights Agent may buy, sell or deal in any of the Rights or other
securities of the Company or become pecuniarily interested in any transaction in
which the Company may be interested, or contract with or lend money to the
Company or otherwise act as fully and freely as though it were not Rights Agent
under this Agreement. Nothing herein shall preclude the Rights Agent from acting
in any other capacity for the Company or for any other legal entity.

            (i) The Rights Agent may execute and exercise any of the rights or
powers hereby vested in it or perform any duty hereunder either itself or by or
through its attorneys or agents, and the Rights Agent shall not be answerable or
accountable for any act, default, neglect or misconduct of any such attorneys or
agents or for any loss to the Company resulting from any such act, default,
neglect or misconduct; provided, however, reasonable care was exercised in the
selection and continued employment thereof.

            (j) No provision of this Agreement shall require the Rights Agent to
expend or risk its own funds or otherwise incur any financial liability in the
performance of any of its duties hereunder or in the exercise of its rights if
there shall be reasonable grounds for believing that repayment of such funds or
adequate indemnification against such risk or liability is not reasonably
assured to it.

            (k) If, with respect to any Right Certificate surrendered to the
Rights Agent for exercise or transfer, the certificate attached to the form of
assignment or form of election to purchase, as the case may be, has either not
been completed or indicates an affirmative response to clause 1 and/or 2
thereof, the Rights Agent shall not take any further action with respect to such
requested exercise of transfer without first consulting with the Company.

      SECTION 21. CHANGE OF RIGHTS AGENT. The Rights Agent or any successor
Rights Agent may resign and be discharged from its duties under this Agreement
upon thirty (30) days' notice in


                                       27
<PAGE>   31
writing mailed to the Company, and to each transfer agent of the Common Stock
and Preferred Stock, by registered or certified mail, and to the holders of the
Rights Certificates by first-class mail. The Company may remove the Rights Agent
or any successor Rights Agent upon thirty (30) days' notice in writing, mailed
to the Rights Agent or successor Rights Agent, as the case may be, and to each
transfer agent of the Common Stock and Preferred Stock, by registered or
certified mail, and to the holders of the Rights Certificates by first-class
mail. If the Rights Agent shall resign or be removed or shall otherwise become
incapable of acting, the Company shall appoint a successor to the Rights Agent.
If the Company shall fail to make such appointment within a period of thirty
(30) days after giving notice of such removal or after it has been notified in
writing of such resignation or incapacity by the resigning or incapacitated
Rights Agent or by the holder of a Rights Certificate (who shall, with such
notice, submit his Rights Certificate for inspection by the Company), then any
registered holder of any Rights Certificate may apply to any court of competent
jurisdiction for an appointment of a new Rights Agent. Any successor Rights
Agent, whether appointed by the Company or by such a court, shall be (a) a
corporation organized and doing business under the law of the United States or
of the State of California (or of any other state of the United States so long
as such corporation is authorized to do business as a banking institution in the
State of California), in good standing, having a principal office in the State
of California, which is authorized under such laws to exercise stock transfer or
corporate trust powers and is subject to supervision or examination by federal
or state authority and which has at the time of its appointment as Rights Agent
a combined capital and surplus of at least $100,000,000, or (b) an Affiliate of
a corporation described in clause (a) of this sentence. After appointment, the
successor Rights Agent shall be vested with the same powers, rights, duties and
responsibilities as if it had been originally named as Rights Agent without
further act or deed; but the predecessor Rights Agent shall deliver and transfer
to the successor Rights Agent any property at the time held by it hereunder, and
execute and deliver any further assurance, conveyance, act or deed necessary for
the purpose. Not later than the effective date of any such appointment, the
Company shall file notice thereof in writing with the predecessor Rights Agent
and each transfer agent of the Common Stock and the Preferred Stock, and mail a
notice thereof in writing to the registered holders of the Rights Certificates.
Failure to give any notice provided for in this Section 21, however, or any
defect therein, shall not affect the legality or validity of the resignation or
removal of the Rights Agent or the appointment of the successor Rights Agent, as
the case may be.

      SECTION 22. ISSUANCE OF NEW RIGHTS CERTIFICATES. Notwithstanding any of
the provisions of this Agreement or of the Rights to the contrary, the Company
may, at its option, issue new Rights Certificates evidencing Rights in such form
as may be approved by its Board of Directors to reflect any adjustment or change
in the Purchase Price and the number or kind or class of shares or other
securities or property purchasable under the Rights Certificates made in
accordance with the provisions of this Agreement. In addition, in connection
with the issuance or sale of shares of Common Stock following the Distribution
Date and prior to the redemption or expiration of the Rights, the Company (a)
shall, with respect to shares of Common Stock so issued or sold pursuant to the
exercise of stock options or under any employee plan or arrangement, or upon the
exercise, conversion or exchange of securities hereinafter issued by the
Company, and (b) may, in any other case, if deemed necessary or appropriate by
the Board of Directors of the Company, issue Rights Certificates representing
the appropriate number of Rights in connection with such issuance or sale;
provided, however, that (i) no such Rights Certificate shall be issued if, and
to the extent that, the Company shall be advised by counsel that such issuance
would create a significant risk of material adverse tax consequences to the
Company or the Person to whom such Rights Certificate would be


                                       28
<PAGE>   32
issued, and (ii) no such Rights Certificate shall be issued if, and to the
extent that appropriate adjustment shall otherwise have been made in lieu of the
issuance thereof.

      SECTION 23. REDEMPTION.

            (a) The Board of Directors of the Company may, at its option, at any
time prior to the earlier of (i) the close of business on the tenth day
following the Stock Acquisition Date, or such later date as may be determined by
action of a majority of Continuing Directors then in office and publicly
announced by the Company (or, if the Stock Acquisition Date shall have occurred
prior to the Record Date, the close of business on the tenth day following the
Record Date, or such later date as may be determined by action of a majority of
Continuing Directors then in office and publicly announced by the Company), or
(ii) the Final Expiration Date, redeem all but not less than all the then
outstanding Rights at a redemption price of $.01 per Right, as such amount may
be appropriately adjusted to reflect any stock split, stock dividend or similar
transaction occurring after the date hereof (such redemption price being
hereinafter referred to as the "Redemption Price"); provided, however, if the
Board of Directors of the Company authorizes redemption of the Rights in either
of the circumstances set forth in clauses (i) and (ii) below, then there must be
Continuing Directors then in office and such authorization shall require the
concurrence of a majority of such Continuing Directors: (i) such authorization
occurs on or after the time a Person becomes an Acquiring Person, or (ii) such
authorization occurs on or after the date of a change (resulting from a proxy or
consent solicitation) in a majority of the directors in office at the
commencement of such solicitation if any Person who is a participant in such
solicitation has stated (or, if upon the commencement of such solicitation, a
majority of the Board of Directors of the Company has determined in good faith)
that such Person (or any of its Affiliates or Associates) intends to take, or
may consider taking, any action which would result in such Person becoming an
Acquiring Person or which would cause the occurrence of a Triggering Event
unless, concurrent with such solicitation, such Person (or one or more of its
Affiliates or Associates) is making a cash tender offer pursuant to a Schedule
14D-1 (or any successor form) filed with the Securities and Exchange Commission
for all outstanding shares of Common Stock not beneficially owned by such Person
(or by its Affiliates or Associates); provided further, however, that if,
following the occurrence of a Stock Acquisition Date and following the
expiration of the right of redemption hereunder but prior to any Triggering
Event, (i) a person who is an Acquiring Person shall have transferred or
otherwise disposed of a number of shares of Common Stock in one transaction or
series of transactions, not directly or indirectly involving the Company, or any
of its Subsidiaries, which did not result in the occurrence of a Triggering
Event such that such Person is thereafter a Beneficial Owner of 15% or less of
the outstanding shares of Common Stock, and (ii) there are no other Persons,
immediately following the occurrence of the event described in clause (i), who
are Acquiring Persons, then the right of redemption herein shall be reinstated
and thereafter be subject to the provisions of this Section 23. Notwithstanding
anything contained in this Agreement to the contrary, a Distribution Date shall
not occur and the Rights shall not be exercisable until such time as the
Company's right of redemption hereunder has expired. The Company may, at its
option, pay the Redemption Price in cash, shares of Common Stock (based on the
"current market price", as defined in Section 11(d)(i) hereof, of the Common
Stock at the time of redemption) or any other form of consideration deemed
appropriate by the Board of Directors.

            (b) Immediately upon the action of the Board of Directors of the
Company ordering the redemption of the Rights, evidence of which shall have been
filed with the Rights Agent and without any further action and without any
notice, the right to exercise the Rights will terminate


                                       29
<PAGE>   33
and the only right thereafter of the holders of Rights shall be to receive the
Redemption Price for each Right so held. Promptly after the action of the Board
of Directors ordering the redemption of the Rights, the Company shall give
notice of such redemption to the Rights Agent and the holders of the then
outstanding Rights by mailing such notice to all such holders at each holder's
last addresses it appears upon the registry books of the Rights Agent or, prior
to the Distribution Date, on the registry books of the Transfer Agent for the
Common Stock. Any notice which is mailed in the manner herein provided shall be
deemed given, whether or not the holder receives the notice. Each such notice of
redemption will state the method by which the payment of the Redemption Price
will be made.

      SECTION 24. EXCHANGE.

            (a) Subject to applicable laws, rules and regulations, and subject
to subsection (c) below, the Company may, at its option, by majority vote of the
Board of Directors and a majority vote of the Continuing Directors, at any time
following the Stock Acquisition Date, exchange all or part of the then
outstanding and exercisable Rights (which shall not include Rights that have
become void pursuant to the provisions of Section 7(e) hereof) for Common Stock
at an exchange ratio of one (1) share of Common Stock per Right, appropriately
adjusted to reflect any stock split, stock dividend or similar transaction
occurring after the date hereof (such exchange ratio being hereinafter referred
to as the "Ratio of Exchange"). Notwithstanding the foregoing, the Board of
Directors shall not be empowered to effect such exchange at any time after any
Person (other than the Company, any Subsidiary of the Company, any employee
benefit plan of the Company or any such Subsidiary, or any entity holding Common
Stock for or pursuant to the terms of any such plan), together with all
Affiliates and Associates of such Person, becomes the Beneficial Owner of 50% or
more of the Common Stock then outstanding.

            (b) Immediately upon the action of the Board of Directors ordering
the exchange of any Rights pursuant to subsection (a) of this Section 24 and
without any further action and without any notice, the right to exercise such
Rights shall terminate and the only right thereafter of a holder of such rights
shall be to receive that number of shares of Common Stock equal to the number of
such Rights held by such holder multiplied by the Ratio of Exchange. The Company
shall give public notice of any such exchange; provided, however, that the
failure to give, or any defect in, such notice shall not affect the validity of
such exchange. The Company shall mail a notice of any such exchange to all of
the holders of such Rights at their last addresses as they appear upon the
registry books of the Rights Agent. Any notice which is mailed in the manner
herein provided shall be deemed given, whether or not the holder receives the
notice. Each such notice of exchange will state the method by which the exchange
of the Common Stock for Rights will be effected and, in the event of any partial
exchange, the number of Rights which will be exchanged. Any partial exchange
shall be effected pro rata based on the number of Rights (other than Rights
which have become void pursuant to the provisions of Section 7(e) hereof) held
by each holder of Rights.

            (c) In the event that there shall not be sufficient shares of Common
Stock issued but not outstanding or authorized but unissued to permit any
exchange of Rights as contemplated in accordance with Section 24(a), the Company
shall either take such action as may be necessary to authorize additional Common
Stock for issuance upon exchange of the Rights or alternatively, at the option
of a majority of the Board of Directors, with respect to each Right (i) pay cash
in an amount equal to the Current Value (as hereinafter defined), in lieu of
issuing Common Stock in exchange therefor, or (ii) issue debt or equity
securities or a combination thereof, having a value equal to the


                                       30
<PAGE>   34
Current Value (as defined below), in lieu of issuing Common Stock in exchange
for each such Right, where the value of such securities shall be determined by a
nationally recognized investment banking firm selected by the Board of Directors
by majority vote of the Board of Directors, or (iii) deliver any combination of
cash, property, Common Stock and/or other securities having a value equal to the
Current Value in exchange for each Right. For purposes of this Section 24(c)
only, the Current Value shall mean the product of the current per share market
price of Common Stock (determined pursuant to Section 11(d) on the date of the
occurrence of the event described above in subparagraph (a)) multiplied by the
number of shares of Common Stock for which the Right otherwise would be
exchangeable if there were sufficient shares available. To the extent that the
Company determines that some action need be taken pursuant to clauses (i), (ii)
or (iii) of this Section 24(c), the Board of Directors may temporarily suspend
the exercisability of the Rights for a period of up to sixty (60) days following
the date on which the event described in Section 24(a) shall have occurred, in
order to seek any authorization of additional shares of Common Stock and/or to
decide the appropriate form of distribution to be made pursuant to the above
provision and to determine the value thereof. In the event of any such
suspension, the Company shall issue a public announcement stating that the
exercisability of the Rights has been temporarily suspended.

            (d) The Company shall not be required to issue fractions of shares
of Common Stock or to distribute certificates which evidence fractional shares
of Common Stock. In lieu of such fractional shares of Common Stock, there shall
be paid to the registered holders of the Rights Certificates with regard to
which such fractional shares of Common Stock would otherwise be issuable, an
amount in cash equal to the same fraction of the current per share market value
of a whole share of Common Stock (as determined pursuant to the second sentence
of Section 11(d) hereof).

            (e) The Company may, at its option, by majority vote of the Board of
Directors, at any time before any Person has become an Acquiring Person,
exchange all or part of the then outstanding Rights for rights of substantially
equivalent value, as determined reasonably and with good faith by the Board of
Directors, based upon the advice of one or more nationally recognized investment
banking firms.

            (f) Immediately upon the action of the Board of Directors ordering
the exchange of any Rights pursuant to subsection (e) of this Section 24 and
without any further action and without any notice, the right to exercise such
Rights shall terminate and the only right thereafter of a holder of such Rights
shall be to receive that number of rights in exchange therefor as has been
determined by the Board of Directors in accordance with subsection (e) above.
The Company shall give public notice of any such exchange; provided, however,
that the failure to give, or any defect in, such notice shall not affect the
validity of such exchange. The Company shall mail a notice of any such exchange
to all of the holders of such Rights at their last addresses as they appear upon
the registry books of the transfer agent for the Common Stock of the Company.
Any notice which is mailed in the manner herein provided shall be deemed given,
whether or not the holder receives the notice. Each such notice of exchange will
state the method by which the exchange of the Rights will be effected.

      SECTION 25. NOTICE OF CERTAIN EVENTS.

            (a) In case the Company shall propose, at any time after the
Distribution Date, (i) to pay any dividend payable in stock of any class to the
holders of Preferred Stock or to make


                                       31
<PAGE>   35
any other distribution to the holders of Preferred Stock (other than a regular
quarterly cash dividend out of earnings or retained earnings of the Company), or
(ii) to offer to the holders of Preferred Stock rights or warrants to subscribe
for or to purchase any additional shares of Preferred Stock or shares of stock
of any class or any other securities, rights or options, or (iii) to effect any
reclassification of its Preferred Stock (other than a reclassification involving
only the subdivision of outstanding shares of Preferred Stock), or (iv) to
effect any consolidation or merger into or with any other Person (other than a
Subsidiary of the Company in a transaction which complies with Section 11(o)
hereof), or to effect any sale or other transfer (or to permit one or more of
its Subsidiaries to effect any sale or other transfer), in one transaction or a
series of related transactions, of more than 50% of the assets or earning power
of the Company and its Subsidiaries (taken as a whole) to any other Person or
Persons (other than the Company and/or any of its Subsidiaries in one or more
transactions each of which complies with Section 11(o) hereof), (v) to effect
the liquidation, dissolution or winding up of the Company, or (vi) to declare or
pay any dividend on the Common Stock payable in Common Stock or to effect a
subdivision, combination or consolidation of the Common Stock (by
reclassification or otherwise than by payment of dividends in Common Stock),
then, in each such case, the Company shall give to each holder of a Rights
Certificate, to the extent feasible and in accordance with Section 26 hereof, a
notice of such proposed action, which shall specify the record date for the
purposes of such stock dividend, distribution of rights or warrants, or the date
on which such reclassification, consolidation, merger, sale, transfer,
liquidation, dissolution, or winding up is to take place and the date of
participation therein by the holders of the shares of Preferred Stock, if any
such date is to be fixed, and such notice shall be so given in the case of any
action covered by clause (i) or (ii) above at least ten (10) days prior to the
record date for determining holders of the shares of Preferred Stock for
purposes of such action, and in the case of any such other action, at least ten
(10) days prior to the date of the taking of such proposed action or the date of
participation therein by the holders of the shares of Preferred Stock whichever
shall be the earlier.

            (b) In case any of the events set forth in Section 11(a)(ii) hereof
shall occur, then, in any such case, (i) the Company shall as soon as
practicable thereafter give to each holder of a Rights Certificate, to the
extent feasible and in accordance with Section 26 hereof, a notice of the
occurrence of such event, which shall specify the event and the consequences of
the event to holders of Rights under Section 11(a)(ii) hereof, and (ii) all
references in the preceding paragraph to Preferred Stock shall be deemed
thereafter to refer to Common Stock and/or, if appropriate, other securities.

      SECTION 26. NOTICES. Notices or demands authorized by this Agreement to be
given or made by the Rights Agent or by the holder of any Rights Certificate to
or on the Company shall be sufficiently given or made if sent by first-class
mail, postage prepaid, addressed (until another address is filed in writing with
the Rights Agent) as follows:

            SONUS Pharmaceuticals, Inc.
            22026 20th Avenue, S.E.
            Suite 102
            Bothell, Washington  98021
            Attention:  Steven C. Quay, M.D, Ph.D., President and Chief
                        Executive Officer

Subject to the provisions of Section 21, any notice or demand authorized by this
Agreement to be given or made by the Company or by the holder of any Rights
Certificate to or on the Rights Agent


                                       32
<PAGE>   36
shall be sufficiently given or made if sent by first-class mail, postage
prepaid, addressed (until another address is filed in writing with the Company)
as follows:

            U.S. Stock Transfer Corporation
            1745 Gardena Avenue
            Second Floor
            Glendale, California  91204
            Attention:  John Stein, President


Notices or demands authorized by this Agreement to be given or made by the
Company or the Rights Agent to the holder of any Rights Certificate (or, if
prior to the Distribution Date, to the holder of certificates representing
shares of Common Stock) shall be sufficiently given or made if sent by
first-class mail, postage prepaid, addressed to such holder at the address of
such holder as shown on the registry books of the Company.

      SECTION 27. SUPPLEMENTS AND AMENDMENTS. Prior to the Distribution Date,
the Company and the Rights Agent shall, if the Company so directs, supplement or
amend any provision of this Agreement without the approval of any holders of
certificates representing shares of Common Stock. From and after the
Distribution Date, the Company and the Rights Agent shall, if the Company so
directs, supplement or amend this Agreement without the approval of any holders
of Rights Certificates in order (i) to cure any ambiguity, (ii) to correct or
supplement any provision contained herein which may be defective or inconsistent
with any other provisions herein, (iii) to shorten or lengthen any time period
hereunder (which lengthening or shortening, following the first occurrence of an
event set forth in clauses (i) and (ii) of the first proviso to Section 23(a)
hereof, shall be effective only if there are Continuing Directors and shall
require the concurrence of a majority of such Continuing Directors), or (iv) to
change or supplement the provisions hereunder in any manner which the Company
may deem necessary or desirable and which shall not adversely affect the
interests of the holders of Rights Certificates (other than an Acquiring Person
or an Affiliate or Associate of an Acquiring Person); provided, however, this
Agreement may not be supplemented or amended to lengthen, pursuant to clause
(iii) of this sentence, (A) a time period relating to when the Rights may be
redeemed at such time as the Rights are not then redeemable, or (B) any other
time period unless such lengthening is for the purpose of protecting, enhancing
or clarifying the rights of, and/or the benefits to, the holders of Rights. Upon
the delivery of a certificate from an appropriate officer of the Company which
states that the proposed supplement or amendment is in compliance with the terms
of this Section 27, the Rights Agent shall execute such supplement or amendment.
Prior to the Distribution Date, the interests of the holders of Rights shall be
deemed coincident with the interests of the holders of Common Stock.

      SECTION 28. SUCCESSORS. All the covenants and provisions of this Agreement
by or for the benefit of the Company or the Rights Agent shall bind and inure to
the benefit of their respective successors and assigns hereunder.

      SECTION 29. DETERMINATIONS AND ACTIONS BY THE BOARD OF DIRECTORS, ETC. For
all purposes of this Agreement, any calculation of the number of shares of
Common Stock outstanding at any particular time, including for purposes of
determining the particular percentage of such outstanding shares of Common Stock
of which any Person is the Beneficial Owner, shall be made in accordance with
the last sentence of Rule 13d-3(d)(1)(i) of the General Rules and Regulations


                                       33
<PAGE>   37
under the Exchange Act. The Board of Directors of the Company (with, where
specifically provided for herein, the concurrence of the Continuing Directors)
shall have the exclusive power and authority to administer this Agreement and to
exercise all rights and powers specifically granted to the Board (with, where
specifically provided for herein, the concurrence of the Continuing Directors)
or to the Company, or as may be necessary or advisable in the administration of
this Agreement, including, without limitation, the right and power to (i)
interpret the provisions of this Agreement, and (ii) make all determinations
deemed necessary or advisable for the administration of this Agreement
(including a determination to redeem or not redeem the Rights or to amend the
Agreement). All such actions, calculations, interpretations and determinations
(including, for purposes of clause (y) below, all omissions with respect to the
foregoing) which are done or made by the Board (with, where specifically
provided for herein, the concurrence of the Continuing Directors) in good faith,
shall (x) be final, conclusive and binding on the Company, the Rights Agent, the
holders of the Rights and all other parties, and (y) not subject the Board or
the Continuing Directors to any liability to the holders of the Rights.

      SECTION 30. BENEFITS OF THIS AGREEMENT. Nothing in this Agreement shall be
construed to give to any person other than the Company, the Rights Agent and the
registered holders of the Rights Certificates (and, prior to the Distribution
Date, registered holders of the Common Stock) any legal or equitable right,
remedy or claim under this Agreement; but this Agreement shall be for the sole
and exclusive benefit of the Company, the Rights Agent and the registered
holders of the Rights Certificates (and, prior to the Distribution Date,
registered holders of the Common Stock).

      SECTION 31. SEVERABILITY. If any term, provision, covenant or restriction
of this Agreement is held by a court of competent jurisdiction or other
authority to be invalid, void or unenforceable, the remainder of the terms,
provisions, covenants and restrictions of this Agreement shall remain in full
force and effect and shall in no way be affected, impaired or invalidated;
provided, however, that notwithstanding anything in this Agreement to the
contrary, if any such term, provision, covenant or restriction is held by such
court or authority to be invalid, void or unenforceable and the Board of
Directors of the Company determines in its good faith judgment that severing the
invalid language from this Agreement would adversely affect the purpose or
effect of this Agreement, the right of redemption set forth in Section 23 hereof
shall be reinstated and shall not expire until the close of business on the
tenth day following the date of such determination by the Board of Directors.

      SECTION 32. GOVERNING LAW. This Agreement, each Right and each Rights
Certificate issued hereunder shall be deemed to be a contract made under the
laws of the State of Delaware and for all purposes shall be governed by and
construed in accordance with the laws of such State applicable to contracts made
and to be performed entirely within such State, except for Sections 18, 19, 20
and 21 hereof which for all purposes shall be governed by and construed in
accordance with the laws of the State of California.

      SECTION 33. COUNTERPARTS.  This Agreement may be executed in any number of
counterparts and each such counterparts shall for all purposes deemed to be an
original, and all such counterparts shall together constitute but one and the
same instrument.

      SECTION 34. DESCRIPTIVE HEADINGS. Descriptive headings of the several
Sections of this Agreement are inserted for convenience only and shall not
control or affect the meaning or construction of any of the provisions hereof.


                                       34
<PAGE>   38
            IN WITNESS WHEREOF, the parties hereto have caused this Agreement to
be duly executed as of the day and year first above written.

                                        SONUS Pharmaceuticals, Inc.,
                                        a Delaware corporation

                                        By: /s/ Steven C. Quay, M.D., Ph.D.
                                            ------------------------------------
                                            Name:  Steven C. Quay, M.D., Ph.D.
                                            Title: President and Chief Executive
                                                   Officer

                                         U.S. STOCK TRANSFER CORPORATION

                                         By: /s/ John Stein
                                             -----------------------------------
                                             Name:   John Stein
                                             Title: President


                                       35
<PAGE>   39
                                    EXHIBIT A

                CERTIFICATE OF DESIGNATION OF RIGHTS, PREFERENCES
                                AND PRIVILEGES OF

                  SERIES A JUNIOR PARTICIPATING PREFERRED STOCK

                                       OF

                           SONUS PHARMACEUTICALS, INC.

             Pursuant to Section 151 of the General Corporation Law
                            of the State of Delaware



      We, Steven C. Quay, M.D., Ph.D. and Gregory Sessler, the President and the
Assistant Secretary, respectively, of SONUS Pharmaceuticals, Inc., a corporation
organized and existing under the General Corporation Law of the State of
Delaware, in accordance with the provisions of Section 103 thereof, DO HEREBY
CERTIFY:

      That pursuant to the authority conferred upon the Board of Directors by
the Certificate of Incorporation of the said Corporation, the said Board of
Directors on July 29, 1996 adopted the following resolution creating a series of
500,000 shares of Preferred Stock designated as Series A Junior Participating
Preferred Stock:

      "RESOLVED, that pursuant to the authority vested in the Board of Directors
of the corporation by the Certificate of Incorporation, the Board of Directors
does hereby provide for the issue of a series of Preferred Stock, $.001 par
value, of the Corporation, to be designated "Series A Junior Participating
Preferred Stock," initially consisting of 500,000 shares and to the extent that
the designations, powers, preferences and relative and other special rights and
the qualifications, limitations and restrictions of the Series A Junior
Participating Preferred Stock are not stated and expressed in the Certificate of
Incorporation, does hereby fix and herein state and express such designations,
powers, preferences and relative and other special rights and the
qualifications, limitations and restrictions thereof, as follows (all terms used
herein which are defined in the Certificate of Incorporation shall be deemed to
have the meanings provided therein):

      Section 1. Designation and Amount. The shares of such series shall be
designated as "Series A Junior Participating Preferred Stock," par value $.001
per share, and the number of shares constituting such series shall be 500,000.

      Section 2.  Dividends and Distributions.

            (A) Subject to the prior and superior right of the holders of any
shares of any series of Preferred Stock ranking prior and superior to the shares
of Series A Junior Participating Preferred Stock with respect to dividends, the
holders of shares of Series A Junior Participating Preferred Stock shall be
entitled to receive when, as and if declared by the Board of Directors out of
funds legally available for the purpose, quarterly dividends payable in cash on
the last day of


                                       1
<PAGE>   40
September, December, March and June in each year (each such date being referred
to herein as a "Quarterly Dividend Payment Date"), commencing on the first
Quarterly Dividend Payment Date after the first issuance of a share or fraction
of a share of Series A Junior Participating Preferred Stock, in an amount per
share (rounded to the nearest cent) equal to, subject to the provision for
adjustment hereinafter set forth, 100 times the aggregate per share amount of
all cash dividends, and 100 times the aggregate per share amount (payable in
kind) of all non-cash dividends or other distributions other than a dividend
payable in shares of Common Stock or a subdivision of the outstanding shares of
Common Stock (by reclassification or otherwise), declared on the Common Stock of
the Corporation (the "Common Stock") since the immediately preceding Quarterly
Dividend Payment Date, or, with respect to the first Quarterly Dividend Payment
Date, since the first issuance of any share or fraction of a share of Series A
Junior Participating Preferred Stock. In the event the Corporation shall at any
time after August 23, 1996 (the "Rights Declaration Date") (i) declare any
dividend on Common Stock payable in shares of Common Stock, (ii) subdivide the
outstanding Common Stock, or (iii) combine the outstanding Common Stock into a
smaller number of shares, then in each such case, the amount to which holders of
shares of Series A Junior Participating Preferred Stock were entitled
immediately prior to such event under the preceding sentence shall be adjusted
by multiplying such amount by a fraction, the numerator of which is the number
of shares of Common Stock outstanding immediately after such event and the
denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event.

            (B) The Corporation shall declare a dividend or distribution on the
Series A Junior Participating Preferred Stock as provided in paragraph (A) above
immediately after it declares a dividend payable in shares of Common Stock).

            (C) Dividends shall begin to accrue and be cumulative on outstanding
shares of Series A Junior Participating Preferred Stock from the Quarterly
Dividend Payment Date next preceding the date of issue of such shares of Series
A Junior Participating Preferred Stock, unless the date of issue of such shares
is prior to the record date for the first Quarterly Dividend Payment Date, in
which case dividends on such shares shall begin to accrue from the date of issue
of such shares, or unless the date of issue is a Quarterly Dividend Payment Date
or is a date after the record date for the determination of holders of shares of
Series A Participating Preferred Stock entitled to receive a quarterly dividend
and before such Quarterly Dividend Payment Date, in either of which events such
dividends shall begin to accrue and be cumulative from such Quarterly Dividend
Payment Date. Accrued but unpaid dividends shall not bear interest. Dividends
paid on the shares of Series A Junior Participating Preferred Stock in an amount
less than the total amount of such dividends at the time accrued and payable on
such shares shall be allocated pro rata on a share-by-share basis among all such
shares at the time outstanding. The Board of Directors may fix a record date for
the determination of holders of shares of Series A Junior Participating
Preferred Stock entitled to receive payment of a dividend or distribution
declared thereon, which record date shall be no more than thirty (30) days prior
to the date fixed for the payment thereof.

      Section 3. Voting Rights. The holders of shares of Series A Junior
Participating Preferred Stock shall have the following voting rights:

            (A) Subject to the provision for adjustment hereinafter set forth,
each share of Series A Junior Participating Preferred Stock shall entitle the
holder thereof to 100 votes on all matters submitted to a vote of the
stockholders of the Corporation. In the event the Corporation shall at any time
after the Rights Declaration Date (i) declare any dividend on Common Stock
payable in


                                       2
<PAGE>   41
shares of Common Stock, (ii) subdivide the outstanding Common Stock, or (iii)
combine the outstanding Common Stock into a smaller number of shares, then in
each such case the number of votes per share to which holders of shares of
Series A Junior Participating Preferred Stock were entitled immediately prior to
such event shall be adjusted by multiplying such number by a fraction, the
numerator of which is the number of shares of Common Stock outstanding
immediately after such event and the denominator of which is the number of
shares of Common Stock that were outstanding immediately prior to such event.

            (B) Except as otherwise provided herein or by law, the holders of
shares of Series A Junior Participating Preferred Stock and the holders of
shares of Common Stock shall vote together as one class on all matters submitted
to a vote of stockholders of the Corporation.

            (C) Except as required by law, holders of Series A Junior
Participating Preferred Stock shall have no special voting rights and their
consent shall not be required (except to the extent they are entitled to vote
with holders of Common stock as set forth herein) for taking any corporate
action.

      Section 4.  Certain Restrictions.

            (A) The Corporation shall not declare any dividend on, make any
distribution on, or redeem or purchase or otherwise acquire for consideration
any shares of Common Stock after the first issuance of a share or fraction of a
share of Series A Junior Participating Preferred Stock unless concurrently
therewith it shall declare a dividend on the Series A Junior Participating
Preferred Stock as required by Section 2 hereof.

            (B) Whenever quarterly dividends or other dividends or distributions
payable on the Series A Junior Participating Preferred Stock as provided in
Section 2 are in arrears, thereafter and until all accrued and unpaid dividends
and distributions, whether or not declared, on shares of Series A Junior
Participating Preferred Stock outstanding shall have been paid in full, the
Corporation shall not:

                  (i) declare or pay dividends on, make any other distributions
on, or redeem or purchase or otherwise acquire for consideration any shares of
stock ranking junior (either as to dividends or upon liquidation, dissolution or
winding up) to the Series A Junior Participating Preferred Stock;

                  (ii) declare or pay dividends on, make any other distributions
on any shares of stock ranking on a parity (either as to dividends or upon
liquidation, dissolution or winding up) with Series A Junior Participating
Preferred Stock, except dividends paid ratably on the Series A Junior
Participating Preferred stock and all such parity stock on which dividends are
payable or in arrears in proportion to the total amounts to which the holders of
all such shares are then entitled;

                  (iii) redeem or purchase or otherwise acquire for
consideration shares of any stock ranking on a parity (either as to dividends or
upon liquidation, dissolution or winding up) with the Series A Junior
Participating Preferred Stock, provided that the Corporation may at any time
redeem purchase or otherwise acquire shares of any such parity stock in exchange
for shares of any stock of the Corporation ranking junior (either as to
dividends or upon dissolution, liquidation or winding up) to the Series A Junior
Participating Preferred Stock;


                                       3
<PAGE>   42
                  (iv) purchase or otherwise acquire for consideration any
shares of Series A Junior Participating Preferred Stock, or any shares of stock
ranking on a parity with the Series A Junior Participating Preferred Stock,
except in accordance with a purchase offer made in writing or by publication (as
determined by the Board of Directors) to all holders of such shares upon such
terms as the Board of Directors, after consideration of the respective annual
dividend rates and other relative rights and preferences of the respective
series and classes, shall determine in good faith will result in fair and
equitable treatment among the respective series or classes.

            (C) The Corporation shall not permit any subsidiary of the
Corporation to purchase or otherwise acquire for consideration any shares of
stock of the Corporation unless the Corporation could, under paragraph (A) of
this Section 4, purchase or otherwise acquire such shares at such time and in
such manner.

      Section 5. Reacquired Shares. Any shares of Series A Junior Participating
Preferred Stock purchased or otherwise acquired by the Corporation in any manner
whatsoever shall be retired and cancelled promptly after the acquisition
thereof. All such shares shall upon their cancellation become authorized but
unissued shares of Preferred Stock and may be reissued as part of a new series
of Preferred Stock to be created by resolution or resolutions of the Board of
Directors, subject to the conditions and restrictions on issuance set forth
herein.

      Section 6.  Liquidation, Dissolution or Winding Up.

            (A) Upon any liquidation (voluntary or otherwise), dissolution or
winding up of the Corporation, no distribution shall be made to the holders of
shares of stock ranking junior (either as to dividends or upon liquidation,
dissolution or winding up) to the Series A Junior Participating Preferred Stock
unless, prior thereto, the holders of shares of Series A Junior Participating
Preferred Stock shall have received an amount equal to accrued and unpaid
dividends and distributions thereon, whether or not declared, to the date of
such payment, plus an amount equal to the greater of (1) $100 per share,
provided that in the event the Corporation does not have sufficient assets,
after payment of its liabilities and distribution to holders of Preferred Stock
ranking prior to the Series A Participating Preferred Stock, available to permit
payment in full of the $100 per share amount, the amount required to be paid
under this Section 6(A)(1) shall, subject to Section 6(B) hereof, equal the
value of the amount of available assets divided by the number of outstanding
shares of Series A Participating Preferred Stock or (2) subject to the
provisions for adjustment hereinafter set forth, 100 times the aggregate per
share amount to be distributed to the holders of Common Stock (the greater of
(1) or (2), the "Series A Liquidation Preference"). In the event the Corporation
shall at any time after the Rights Declaration Date (i) declare any dividend on
Common Stock payable in shares of Common Stock, (ii) subdivide the outstanding
Common Stock, or (iii) combine the outstanding Common Stock into a smaller
number of shares, then in each such case the amount to which holders of shares
of Series A Junior Participating Preferred Stock were entitled immediately prior
to such event under clause (2) of the preceding sentence shall be adjusted by
multiplying such amount by a fraction the numerator of which is the number of
shares of Common Stock that were outstanding immediately after such event and
the denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event.

            (B) In the event, however, that there are not sufficient assets
available to permit payment in full of the Series A Liquidation Preference and
the liquidation preferences of all other series of Preferred Stock, if any,
which rank on a parity with the Series A Junior Participant


                                       4
<PAGE>   43
Preferred Stock, then such remaining assets shall be distributed ratably to the
holders of such parity shares in proportion to their respective liquidation
preferences.

      Section 7. Consolidation, Merger, etc. In case the Corporation shall enter
into any consolidation, merger, combination or other transaction in which the
shares of Common Stock are exchanged for or changed into other stock or
securities, cash and/or any other property, then in any such case the shares of
Series A Participating Preferred Stock shall at the same time be similarly
exchanged or changed in amount per share (subject to the provision for
adjustment hereinafter set forth) equal to 100 times the aggregate amount of
stock, securities, cash and/or any other property (payable in kind), as the case
may be, into which or for which each share of Common Stock is changed or
exchanged. In the event the Corporation shall at any time after the Rights
Declaration Date (i) declare any dividend on Common Stock payable in shares of
Common Stock, (ii) subdivide the outstanding Common Stock, or (iii) combine the
outstanding Common Stock into a smaller number of shares, then in each such case
the amount set forth in the preceding sentence with respect to the exchange or
change of shares of Series A Junior Participating Preferred Stock shall be
adjusted by multiplying such amount by a fraction the numerator of which is the
number of shares of Common Stock outstanding immediately after such event and
the denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event.

      Section 8. No Redemption. The shares of Series A Junior Participating
Preferred Stock shall not be redeemable.

      Section 9. Ranking. The Series A Junior Participating Preferred Stock
shall rank junior to all other series of the Corporation's Preferred Stock as to
the payment of dividends and the distribution of assets, unless the terms of any
such series shall provide otherwise.

      Section 10. Amendment. The Certificate of Incorporation of the Corporation
shall not be further amended in any manner which would materially alter or
change the powers, preference or special rights of the Series A Junior
Participating Preferred Stock so as to affect them adversely without the
affirmative vote of the holders of a majority or more of the outstanding shares
of Series A Junior Participating Preferred Stock, voting separately as a class.

      Section 11. Fractional Shares. Series A Junior Participating Preferred
Stock may be issued in fractions of a share which shall entitle the holder, in
proportion to such holder's fractional shares, to exercise voting rights,
receive dividends, participate in distributions and to have the benefit of all
other rights of holders of Series A Junior Participating Preferred Stock.


                                       5
<PAGE>   44
      IN WITNESS WHEREOF, we have executed and subscribed this Certificate and
do affirm the foregoing as true under the penalties of perjury this 23rd day of
August, 1996.

                                      __________________________________________
                                      Steven C. Quay, M.D., Ph.D., President and
                                      Chief Executive Officer

ATTEST:

____________________________________
Gregory Sessler, Assistant Secretary


                                       6
<PAGE>   45
                                    EXHIBIT B

                           Form of Rights Certificate

Certificate No. R-                                                 ______ Rights

      NOT EXERCISABLE AFTER ____________, ______ OR EARLIER IF TERMINATED BY THE
      COMPANY. THE RIGHTS ARE SUBJECT TO REDEMPTION, AT THE OPTION OF THE
      COMPANY, AT $.01 PER RIGHT ON THE TERMS SET FORTH IN THE RIGHTS AGREEMENT.
      UNDER CERTAIN CIRCUMSTANCES, RIGHTS BENEFICIALLY OWNED BY AN ACQUIRING
      PERSON OR AN AFFILIATE OR ASSOCIATE OF AN ACQUIRING PERSON (AS SUCH TERMS
      ARE DEFINED IN THE RIGHTS AGREEMENT) AND ANY SUBSEQUENT HOLDER OF SUCH
      RIGHTS MAY BECOME NULL AND VOID. [THE RIGHTS REPRESENTED BY THIS RIGHTS
      CERTIFICATE ARE OR WERE BENEFICIALLY OWNED BY A PERSON WHO WAS OR BECAME
      AN ACQUIRING PERSON OR AN AFFILIATE OR ASSOCIATE OF AN ACQUIRING PERSON
      (AS SUCH TERMS ARE DEFINED IN THE RIGHTS AGREEMENT). ACCORDINGLY, THIS
      RIGHTS CERTIFICATE AND THE RIGHTS REPRESENTED HEREBY MAY BECOME NULL AND
      VOID IN THE CIRCUMSTANCES SPECIFIED IN SECTION 7(e) OF SUCH RIGHTS
      AGREEMENT.]*

                               Rights Certificate

      This certifies that ____________, or registered assigns, is the registered
owner of the number of Rights set forth above, each of which entitles the owner
thereof, subject to the terms, provisions and conditions of the Rights
Agreement, dated as of August 23, 1996 as such agreement may be amended from
time to time in accordance with its terms (the "Rights Agreement"), between
SONUS Pharmaceuticals, Inc., a Delaware corporation (the "Company"), and U.S.
Stock Transfer Corporation (the "Rights Agent"), to purchase from the Company at
any time after the Distribution Date (as such term is defined in the Rights
Agreement) and prior to 5:00 P.M., East Coast time, on August 23, 2006 at the
office of the Rights Agent designated for such purpose, or at the office of its
successor as Rights Agent, one one-hundredth of a fully paid non-assessable
share of Series A Junior Participating Preferred Stock (the "Preferred Shares"),
of the Company, at a purchase price of $140 per one one-hundredth of a Preferred
Share (the "Purchase Price"), upon presentation and surrender of this Rights
Certificate with the form of Election to Purchase and related Certificate duly
executed. The number of Rights evidenced by this Rights Certificate (and the
number of one-hundredths of a Preferred Share which may be purchased upon
exercise hereof) set forth above, are the number and Purchase Price as of August
23, 1996, based on the Preferred Shares as constituted at such date. As provided
in the Rights Agreement, the Purchase Price and the number and kind of Preferred
Shares or other securities which may be purchased upon the exercise of the
Rights evidenced by this Rights Certificate are subject to modification and
adjustment upon the happening of certain events.

- ------------------------
      *     The portion of the legend in bracket shall be inserted only if
            applicable and shall replace the preceding sentence.
<PAGE>   46
      This Rights Certificate is subject to all of the terms, provisions and
conditions of the Rights Agreement, which terms, provisions and conditions are
hereby incorporated herein by reference and made a part hereof and to which
Rights Agreement reference is hereby made for a full description of the rights,
limitations of rights, obligations, duties and immunities hereunder of the
Rights Agent, the Company and the holders of the Rights Certificates, which
limitations of rights include the temporary suspension of the exercisability of
such Rights under the specific circumstances set forth in the Rights Agreement.
Copies of the Rights Agreement are on file at the principal executive offices of
the Company and the above-mentioned office of the Rights Agent.

      Subject to the provisions of the Rights Agreement, the Rights evidenced by
this Rights Certificate (i) may be redeemed by the Company, at its option, at a
redemption price of $.01 per Right or (ii) may be exchanged by the Company in
whole or in part for Common Shares, substantially equivalent rights or other
consideration as determined by the Company.

       This Rights Certificate, with or without other Rights Certificates, upon
surrender at the office of the Rights Agent designated for such purpose may be
exchanged for another Rights Certificate or Rights Certificates of like tenor
and date evidencing Rights entitling the holder to purchase a like aggregate
amount of securities as the Rights evidenced by the Rights Certificate or Rights
Certificates surrendered shall have entitled such holder to purchase. If this
Rights Certificate shall be exercised in part, the holder shall be entitled to
receive upon surrender hereof another Rights Certificate or Rights Certificates
for the number of whole Rights not exercised.

      No fractional portion less than integral multiples of one one-hundredth of
a Preferred Share will be issued upon the exercise of any Right or Rights
evidenced hereby but in lieu thereof a cash payment will be made, as provided in
the Rights Agreement.

      No holder of this Rights Certificate, as such, shall be entitled to vote
or receive dividends or be deemed for any purpose the holder of the Preferred
Shares or any other securities of the Company which may at any time be issuable
on the exercise hereof, nor shall anything contained in the Rights Agreement or
herein be construed to confer upon the holder hereof, as such, any of the rights
of a stockholder of the Company or any right to vote for the election of
directors or upon any matter submitted to stockholders at any meeting thereof,
or to give or withhold consent to any corporate action, or to receive notice of
meetings or other actions affecting stockholders (except as provided in the
Rights Agreement), or to receive dividends or subscription rights, or otherwise,
until the Right or Rights evidenced by this Rights Certificate shall have been
exercised as provided in the Rights Agreement.

      The Rights Certificate shall not be valid or obligatory for any purpose
until it shall have been countersigned by the Rights Agent.


                                       2
<PAGE>   47
      WITNESS the facsimile signature of the proper officers of the Company and
its corporate seal. Dated as of _________, _____.

ATTEST:                                   SONUS PHARMACEUTICALS, INC.

____________________________________      By:___________________________________
Gregory Sessler, Assistant Secretary         Steven C. Quay, M.D., Ph.D.,
                                             President and
                                             Chief Executive Officer

Countersigned:

U.S. STOCK TRANSFER CORPORATION
as Rights Agent

By: ________________________________
    Authorized Signature


                                       3
<PAGE>   48
                   Form of Reverse Side of Rights Certificate

                               FORM OF ASSIGNMENT

                (To be executed by the registered holder if such
               holder desires to transfer the Rights Certificate)

      FOR VALUE RECEIVED________________________________________________________
hereby sells, assigns and transfers unto________________________________________
________________________________________________________________________________
                  (Please print name and address of transferee)

this Rights Certificate, together with all right, title and interest therein,
and does hereby irrevocably constitute and appoint Attorney, to transfer the
within Rights Certificate on the books of the within-named Company, with full
power of substitution.

Dated: ___________________, __

                                    ____________________________________________
                                    Signature

Signature Guaranteed:

      The signatures should be guaranteed by an eligible guarantor institution
(banks, stock brokers, savings and loan associations and credit unions with
members in an approved signature guarantee medallion program) pursuant to S.E.C.
Rule 17Ad-15.


                                       4
<PAGE>   49
                                   CERTIFICATE

      The undersigned hereby certifies by checking the appropriate boxes that:

            (1) this Rights Certificate [ ] is [ ] is not being sold, assigned
and transferred by or on behalf of a Person who is or was an Acquiring Person,
or an Affiliate or Associate of any such Person (as such terms are defined in
the Rights Agreement);

            (2) after due inquiry and to the best knowledge of the undersigned,
it [ ] did [ ] did not acquire the Rights evidenced by this Rights Certificate
from any Person who is, was or subsequently became an Acquiring Person or an
Affiliate or Associate of any such Person.

Dated: ___________________, __

                                    ____________________________________________
                                    Signature

Signature Guaranteed:

      The signatures should be guaranteed by an eligible guarantor institution
(banks, stock brokers, savings and loan associations and credit unions with
members in an approved signature guarantee medallion program) pursuant to S.E.C.
Rule 17Ad-15.


                                       5
<PAGE>   50
             Form of Reverse Side of Rights Certificate -- continued

                          FORM OF ELECTION TO PURCHASE

      (To be executed if holder desires to exercise the Rights Certificate)

To:________________________________

      The undersigned hereby irrevocable elects to exercise_____________________
Rights represented by this Rights Certificate to purchase the number of
one-hundredths of a Preferred Share issuable upon the exercise of such Rights
and requests that certificates for such number of one-hundredths of a Preferred
Share be issued in the name of:

Please insert social security or other identifying number

________________________________________________________________________________
                         (Please print name and address)
________________________________________________________________________________

If such number of Rights shall not be all the Rights evidenced by this Rights
Certificate, a new Rights Certificate for the balance remaining of such Rights
shall be registered in the name of and delivered to:

Please insert social security or other identifying number

________________________________________________________________________________
                        (Please print name and address)
________________________________________________________________________________

Dated: ___________________, __

                                    ____________________________________________
                                    Signature

Signature Guaranteed:

      The signatures should be guaranteed by an eligible guarantor institution
(banks, stock brokers, savings and loan associations and credit unions with
members in an approved signature guarantee medallion program) pursuant to S.E.C.
Rule 17Ad-15.


                                       6
<PAGE>   51
                                   CERTIFICATE

      The undersigned hereby certifies by checking the appropriate boxes that:

            (1) this Rights Certificate [ ] is [ ] is not being sold, assigned
and transferred by or on behalf of a Person who is or was an Acquiring Person,
or an Affiliate or Associate of any such Person (as such terms are defined in
the Rights Agreement);

            (2) after due inquiry and to the best knowledge of the undersigned,
it [ ] did [ ] did not acquire the Rights evidenced by this Rights Certificate
from any Person who is, was or subsequently became an Acquiring Person or an
Affiliate or Associate of any such Person.



Dated: ___________________, __

                                    ____________________________________________
                                    Signature

Signature Guaranteed:

      The signatures should be guaranteed by an eligible guarantor institution
(banks, stock brokers, savings and loan associations and credit unions with
members in an approved signature guarantee medallion program) pursuant to S.E.C.
Rule 17Ad-15.


                                       7
<PAGE>   52
             Form of Reverse Side of Rights Certificate -- continued

                                     NOTICE

      The signature in the foregoing Forms of Assignment and Election must
conform to the name as written upon the face of this Rights Certificate in every
particular, without alteration or enlargement or any change whatsoever.


                                       8
<PAGE>   53
                               Rights Certificate

Certificate No. R-                                                 ______ Rights

      NOT EXERCISABLE AFTER ____________, _____ OR EARLIER IF TERMINATED BY THE
      COMPANY. THE RIGHTS ARE SUBJECT TO REDEMPTION, AT THE OPTION OF THE
      COMPANY, AT $.01 PER RIGHT ON THE TERMS SET FORTH IN THE RIGHTS AGREEMENT.
      UNDER CERTAIN CIRCUMSTANCES, RIGHTS BENEFICIALLY OWNED BY AN ACQUIRING
      PERSON OR AN AFFILIATE OR ASSOCIATE OF AN ACQUIRING PERSON (AS SUCH TERMS
      ARE DEFINED IN THE RIGHTS AGREEMENT) AND ANY SUBSEQUENT HOLDER OF SUCH
      RIGHTS MAY BECOME NULL AND VOID. [THE RIGHTS REPRESENTED BY THIS RIGHTS
      CERTIFICATE ARE OR WERE BENEFICIALLY OWNED BY A PERSON WHO WAS OR BECAME
      AN ACQUIRING PERSON OR AN AFFILIATE OR ASSOCIATE OF AN ACQUIRING PERSON
      (AS SUCH TERMS ARE DEFINED IN THE RIGHTS AGREEMENT). ACCORDINGLY, THIS
      RIGHTS CERTIFICATE AND THE RIGHTS REPRESENTED HEREBY MAY BECOME NULL AND
      VOID IN THE CIRCUMSTANCES SPECIFIED IN SECTION 7(e) OF SUCH RIGHTS
      AGREEMENT.]**

                               Rights Certificate

      This certifies that ______________, or registered assigns, is the
registered owner of the number of Rights set forth above, each of which entitles
the owner thereof, subject to the terms, provisions and conditions of the Rights
Agreement, dated as of August 23, 1996 as such agreement may be amended from
time to time in accordance with its terms (the "Rights Agreement"), between
SONUS Pharmaceuticals, Inc., a Delaware corporation (the "Company"), and U.S.
Stock Transfer Corporation (the "Rights Agent"), to purchase from the Company at
any time after the Distribution Date (as such term is defined in the Rights
Agreement) and prior to 5:00 P.M., East Coast time, on August 23, 2006 at the
office of the Rights Agent designated for such purpose, or at the office of its
successor as Rights Agent, one one-hundredth of a fully paid non-assessable
share of Series A Junior Participating Preferred Stock (the "Preferred Shares"),
of the Company, at a purchase price of $140 per one one-hundredth of a Preferred
Share (the "Purchase Price"), upon presentation and surrender of this Rights
Certificate with the form of Election to Purchase and related Certificate duly
executed. The number of Rights evidenced by this Rights Certificate (and the
number of one-hundredths of a Preferred Share which may be purchased upon
exercise hereof) set forth above, are the number and Purchase Price as of August
23, 1996, based on the Preferred Shares as constituted at such date. As provided
in the Rights Agreement, the Purchase Price and the number and kind of Preferred
Shares or other securities which may be purchased upon the exercise of the
Rights evidenced by this Rights Certificate are subject to modification and
adjustment upon the happening of certain events.

- ------------------------
      **    The portion of the legend in bracket shall be inserted only if
            applicable and shall replace the preceding sentence.


                                       9
<PAGE>   54
                                    EXHIBIT C

                                SUMMARY OF TERMS
                           SHAREHOLDER RIGHTS PLAN FOR

                           SONUS PHARMACEUTICALS, INC.

      On July 29, 1996, the Board of Directors of SONUS Pharmaceuticals, Inc.
(the "Corporation") approved the adoption of a Shareholder Rights Plan and on
September 3, 1996 declared a dividend distribution of one Right for each
outstanding share of SONUS Pharmaceuticals, Inc. Common Stock to stockholders of
record on the close of business on August 23, 1996 (the "Dividend Date"). Each
Right entitles the registered holder to purchase from the Corporation a unit
consisting of one one-hundredth of a share (a "Unit") of Series A Junior
Participating Preferred Stock, par value $0.001 per share (the "Preferred
Stock"), at a purchase price of $140 per Unit, subject to adjustment. The
description and terms of the Rights are set forth in a Rights Agreement (the
"Rights Agreement") between the Corporation and U.S. Stock Transfer Corporation,
as Rights Agent.

            Certificates. Initially, the Rights will be attached to all Common
Stock certificates representing shares then outstanding, and no separate Rights
Certificates will be distributed. Subject to extension by the Board of Directors
in certain circumstances, the Rights will separate from the Common Stock and a
distribution date (the "Distribution Date") will occur upon the earlier of (i)
10 days following a public announcement that a person or group of affiliated or
associated persons (an "Acquiring Person") has acquired, or obtained the right
to acquire, beneficial ownership of 15% or more of the outstanding shares of
Common Stock (the "Stock Acquisition Date"); or (ii) 10 business days following
the commencement of a tender offer or exchange offer that would result in a
person or group beneficially owning 15% or more of the outstanding shares of
Common Stock. Current 15% stockholders are excluded from the definition of an
Acquiring Person until their respective beneficial ownership exceeds 30% or more
of the outstanding shares of Common Stock. Until the Distribution Date, (i) the
Rights will be evidenced by the Common Stock certificates and will be
transferred with and only with such Common Stock certificates; (ii) new Common
Stock certificates issued will contain a notation incorporating the Rights
Agreement by reference; and (iii) the surrender for transfer of any certificates
for Common Stock outstanding will also constitute the transfer of the Rights
associated with the Common Stock represented by such certificate.

            Expiration and Exercise. The Rights are not exercisable until the
Distribution Date and will expire at the close of business on August 23, 2006,
unless earlier redeemed by the Corporation as described below.

            As soon as practicable after the Distribution Date, Rights
Certificates will be mailed to holders of record of the Common Stock as of the
close of business on the Distribution Date and, thereafter, the separate Rights
Certificates will represent the Rights. Except as otherwise determined by the
Board of Directors, only shares of Common Stock issued prior to the Distribution
Date will be issued with Rights.

            "Flip-In". In the event that, at any time following the Dividend
Date, (i) the Corporation is the surviving corporation in a merger with an
Acquiring Person and its Common


                                       1
<PAGE>   55
Stock is not changed or exchanged; (ii) an Acquiring Person becomes the
beneficial owner of more than 15% of the outstanding shares of Common Stock;
(iii) an Acquiring Person engages in one or more "self-dealing" transactions as
set forth in the Rights Agreement; or (iv) during such time as there is an
Acquiring Person, an event occurs which results in such Acquiring Person's
ownership interest being increased by more than 1% (e.g., a reverse stock
split), each holder of a Right will thereafter have the right to receive, upon
exercise, Common Stock (or, in certain circumstances, cash, property or other
securities of the Corporation) having a value equal to two times the exercise
price of the Right. Notwithstanding any of the foregoing, following the
occurrence of any of the events set forth in this paragraph, all Rights that
are, or (under certain circumstances specified in the Rights Agreement) were,
beneficially owned by any Acquiring Person will be null and void. However,
Rights are not exercisable following the occurrence of any of the events set
forth above until such time as the Rights are no longer redeemable by the
Corporation as set forth below.

            For example, at an exercise price of $140 per Right, each Right not
owned by an Acquiring Person (or by certain related parties) following an event
set forth in the preceding paragraph would entitle its holder to purchase $280
worth of Common Stock (or other consideration, as noted above) for $140.
Assuming that the Common Stock had a per share value of $40 at such time, the
holder of each valid Right would be entitled to purchase 7 shares of Common
Stock for $140.

            Permitted Offer. A tender or exchange offer for all outstanding
Common Stock at a price and on terms determined by the Board of Directors prior
to the purchase to be adequate and in the best interests of the Corporation and
its stockholders (other than the Acquiring Person) is a Permitted Offer under
the Rights Agreement. A Permitted Offer does not trigger the exercisability of
the Rights.

            "Flip-Over". In the event that, at any time following the Stock
Acquisition Date, (i) the Corporation is acquired in a merger or other business
combination transaction in which the Corporation is not the surviving
corporation; or (ii) 50% or more of the Corporation's assets or earning power is
sold or transferred, each holder of a Right (except Rights which previously have
been voided as set forth above) shall thereafter have the right to receive, upon
exercise, common stock of the acquiring company having a value equal to two
times the exercise price of the Right. The events set forth in this paragraph
and in the third preceding paragraph are referred to as the "Triggering Events."

            Exchange Feature. At any time after any Person becomes an Acquiring
Person and prior to the acquisition by such person or group of 50% or more of
the outstanding Common Stock, the Board of Directors may exchange the Rights
(other than Rights owned by such Person or group which will have become void),
in whole or in part, at an exchange rate of one share of Common Stock (or a
combination of cash, property, Common Stock or other securities having an equal
value) per Right (subject to adjustment).

            Adjustment for Dilution. The purchase price payable, and the number
of Units of Preferred Stock or other securities or property issuable upon
exercise of the Rights are subject to adjustment from time to time to prevent
dilution (i) in the event of a stock dividend on, or a subdivision, combination
or reclassification of, the Preferred Stock; (ii) if holders of the Preferred
Stock are granted certain rights or warrants to subscribe for Preferred Stock or
convertible securities at less than the current market price of the Preferred
Stock; or (iii) upon the distribution to holders


                                       2
<PAGE>   56
of the Preferred Stock of evidences of indebtedness or assets (excluding regular
quarterly cash dividends) or of subscription rights or warrants (other than
those referred to above).

            With certain exceptions, no adjustment in the purchase price will be
required until cumulative adjustments amount to at least 1% of the purchase
price. No fractional Units will be issued and, in lieu thereof, an adjustment in
cash will be made based on the market price of the Preferred Stock on the last
trading date prior to the date of exercise.

            Redemption. At any time until ten days following the Stock
Acquisition Date (subject to extension by the Continuing Directors, as defined
below), the Corporation may redeem the Rights in whole, but not in part, at a
price of $.01 per Right. Under certain circumstances set forth in the Rights
Agreement, the decision to redeem shall require the concurrence of a majority of
the Continuing Directors. After the redemption period has expired, the
Corporation's right of redemption may be reinstated if an Acquiring Person
reduces his beneficial ownership to 15% or less of the outstanding shares of the
Common Stock in a transaction or series of transactions not involving the
Corporation. Immediately upon the action of the Board of Directors ordering
redemption of the Rights, with (where required) the concurrence of the
Continuing Directors, the Rights will terminate and the only right of the
holders of Rights will be to receive the $.01 redemption price. Rights are not
exercisable while subject to redemption.

            Continuing Directors. The term "Continuing Directors" means any
member of the Board of Directors of the Corporation who was a member of the
Board prior to the date of the Rights Agreement, and any person who is
subsequently elected to the Board if such person is recommended or approved by a
majority of the Continuing Directors, but shall not include an Acquiring Person,
or an affiliate or associate of an Acquiring Person, or any representative of
the foregoing entities.

            Stockholder Rights. Until a Right is exercised, the holder thereof,
as such, will have no rights as a stockholder of the Corporation, including,
without limitation, the right to vote or to receive dividends. While the
distribution of the Rights will not be taxable to stockholders or to the
Corporation, stockholders may, depending upon the circumstances, recognize
taxable income in the event that the Rights become exercisable for Common Stock
(or other consideration) of the Corporation or for common stock of the acquiring
company as set forth above.

            Amendments. Any of the provisions of the Rights Agreement may be
amended by the Board of Directors of the Corporation prior to the Distribution
Date. After the Distribution Date, the provisions of the Rights Agreement may be
amended by the Board (in certain circumstances, with the concurrence of the
Continuing Directors) in order to cure any ambiguity, to make changes which do
not adversely affect the interests of holders of Rights (excluding the interests
of any Acquiring Person), or to shorten or lengthen any time period under the
Rights Agreement; provided, however, that no amendment to adjust the time period
governing redemption shall be made at such time as the Rights are not
redeemable.

            Availability of Rights Agreement. A copy of the Rights Agreement has
been filed with the Securities and Exchange Commission as an Exhibit to a
Registration Statement on form 8-A dated August 23, 1996. A copy of the Rights
Agreement is available free of charge from the Corporation. This Summary of
Terms does not purport to be complete and is qualified in its entirety by
reference to the Rights Agreement, which is incorporated herein by reference.


                                       3


© 2022 IncJournal is not affiliated with or endorsed by the U.S. Securities and Exchange Commission