<PAGE>
<TABLE>
<S> <C>
PROSPECTUS SUPPLEMENT FILED PURSUANT TO RULE 424(b)(3)
(TO PROSPECTUS DATED JULY 28, 1999) REGISTRATION NO. 333-75561
</TABLE>
SEPRACOR INC.
---------------
$300,000,000 PRINCIPAL AMOUNT OF
7% CONVERTIBLE SUBORDINATED DEBENTURES
DUE 2005
------------------
2,402,402 SHARES OF COMMON STOCK
$0.10 PAR VALUE PER SHARE
The information in this prospectus supplement concerning the Selling
Securityholders supplements the statements set forth under the caption "Selling
Securityholders" in the prospectus. Capitalized items used and not defined
herein shall have the meanings given to them in the prospectus. The information
set forth under the caption "Selling Securityholders" in the prospectus is
supplemented as follows:
SELLING SECURITYHOLDERS
We originally sold the debentures on December 15, 1998 to Morgan Stanley
Dean Witter and Salomon Smith Barney. These initial purchasers of the debentures
have advised us that the debentures were resold in transactions exempt from the
registration requirements of the Securities Act to "qualified institutional
buyers," defined in Rule 144A of the Securities Act. These subsequent
purchasers, or their transferees, pledges, donees or successors, may from time
to time offer and sell any or all of the debentures and/or shares of the common
stock issuable upon conversion of the debentures pursuant to this prospectus.
The debentures and the shares of common stock issuable upon conversion of
the debentures have been registered pursuant to the registration rights
agreement. Pursuant to the registration rights agreement, we are required to
file a registration statement with regard to the debentures and the shares of
our common stock issuable upon conversion of the debentures and to keep the
registration statement effective until the earlier of:
(1) the sale of all the securities registered pursuant to the registration
rights agreement, and
(2) the expiration of the holder period applicable to these securities under
Rule 144(k) under the Securities Act or any successor provision.
The selling securityholders may choose to sell debentures and/or the shares
of common stock issuable upon conversion of the debentures from time to time.
See "Plan of Distribution."
The following table sets forth:
(1) the name of each selling securityholder who has provided us with notice
as of the date of this prospectus pursuant to the registration rights
agreement of their intent to sell or otherwise dispose of debentures
and/or shares of common stock issuable upon conversion of the debentures
pursuant to the registration statement,
(2) the principal amount of the debentures and the number of shares of our
common stock issuable upon conversion of the debentures which they may
sell from time to time pursuant to the registration statement, and
(3) the amount of outstanding debentures and our common stock beneficially
owned by the selling securityholder prior to the offering, assuming no
conversion of the debentures.
To our knowledge, no selling securityholder nor any of its affiliates had
held any position or office with, been employed by or otherwise has had any
material relationship with Sepracor or Sepracor's affiliates, during the three
years prior to the date of this prospectus.
<PAGE>
A selling securityholder may offer all or some portion of the debentures and
shares of the common stock issuable upon conversion of the debentures.
Accordingly, no estimate can be given as to the amount or percentage of
debentures or our common stock that will be held by the selling securityholders
upon termination of sales pursuant to this prospectus. In addition, the selling
securityholders identified below may have sold, transferred or disposed of all
or a portion of their debentures since the date on which they provided the
information regarding their holdings in transactions exempt from the
registration requirements of the Securities Act.
The information contained under the column heading "Shares That May be Sold"
assumes conversion of full amount of the debentures held by the holder at the
adjusted rate of $62.4375 in principal amount of the debentures per share of the
common stock.
<TABLE>
<CAPTION>
AMOUNT OF 7% AMOUNT OF 7% SHARES OF
DEBENTURES THAT DEBENTURES OWNED SHARES THAT COMMON STOCK OWNED
NAME MAY BE SOLD BEFORE OFFERING MAY BE SOLD BEFORE OFFERING
---- --------------- ---------------- ----------- ------------------
<S> <C> <C> <C> <C>
Aloha Airlines Non-Pilots
Pension Trust................. $ 250,000 $ 250,000 4,004 0
Aloha Airlines Pilots Retirement
Trust......................... 125,000 125,000 2,002 0
Aloha Airlines Non-Pilots
Pension Trust................. 185,000 185,000 2,962 0
Amoco Corporation Master Trust
for Employee Pension Plans.... 2,962,000 2,962,000 47,439 0
Arkansas Teachers Retirement.... 3,605,000 3,605,000 57,737 0
Associated Electric & Gas
Insurance Services Limited.... 1,200,000 1,200,000 19,219 0
Baptist Health of South
Florida....................... 368,000 368,000 5,893 0
Bank of America................. 250,000 250,000 4,004 0
Bankroft Convertible Fund,
Inc........................... 1,000,000 1,000,000 16,016 0
Bear Stearns & Co............... 4,000,000 4,000,000 64,064 0
Boston Museum of Fine Arts...... 255,000 255,000 4,084 0
Boulder II Limited.............. 150,000 150,000 2,402 0
Boulder Capital Inc............. 358,000 358,000 5,733 0
BNP Arbitrage SNC............... 50,000 50,000 800 24,850
BTES Convertible Arb............ 2,300,000 2,300,000 36,836 0
CA Public Employees' Retirement
System........................ 9,000,000 9,000,000 144,144 0
Castle Convertible Fund, Inc.... 250,000 250,000 4,004 0
C&H Sugar Company, Inc.......... 300,000 300,000 4,804 0
Capital Market Transactions
Inc........................... 4,000,000 4,000,000 64,064 0
Chrysler Corporation Master
Retirement Trust.............. 5,665,000 5,665,000 90,730 0
CIBC World Markets International
Equity Arbitrage.............. 1,000,000 1,000,000 16,016 0
Citizens Security Life Ins.
Co............................ 1,000,000 1,000,000 16,016 0
CNA Income Shares, Inc.......... 750,000 750,000 12,012 0
Continental Assurance Company... 5,200,000 5,200,000 83,283 0
Declaration of Trust for the
Defined Benefit Plans of ICI
American Holdings Inc......... 1,050,000 1,050,000 16,816 0
Declaration of Trust for the
Defined Benefit Plans of
Zeneca Holdings Inc........... 710,000 710,000 11,371 0
Delaware PERS................... 1,575,000 1,575,000 25,225 0
</TABLE>
<PAGE>
<TABLE>
<CAPTION>
AMOUNT OF 7% AMOUNT OF 7% SHARES OF
DEBENTURES THAT DEBENTURES OWNED SHARES THAT COMMON STOCK OWNED
NAME MAY BE SOLD BEFORE OFFERING MAY BE SOLD BEFORE OFFERING
---- --------------- ---------------- ----------- ------------------
<S> <C> <C> <C> <C>
Delaware State Employees'
Retirement Fund............... 1,430,000 1,430,000 22,902 0
Delta Air Lines Master Trust.... 2,495,000 2,495,000 39,959 0
Deutsche Bank Securities........ 29,000,000 29,000,000 464,464 0
Dunham & Associates III......... 216,000 216,000 3,459 0
Ellsworth Convertible Growth and
Income Fund, Inc.............. 1,000,000 1,000,000 16,016 0
Engineers Joint Pension Fund.... 694,000 694,000 11,115 0
Family Service Life Insurance
Company....................... 600,000 600,000 9,609 0
GCG Trust Fully Managed 215,000 215,000 3,443 0
Goldman Sachs and Company....... 2,545,000 2,545,000 40,760 0
Grenfell, Gabrielle............. 50,000 50,000 800 0
Greyhound Lines................. 100,000 100,000 1,601 0
Hamilton Partners Limited....... 2,000,000 2,000,000 32,032 0
Hawaiian Airlines Employees
Pension Plan--IAM............. 200,000 200,000 3,203 0
Hawaiian Airlines Pension Plan
for Salaried Employees........ 50,000 50,000 800 0
Hawaiian Airlines Pilots
Retirement Plan............... 275,000 275,000 4,404 0
Highbridge Capital
Corporation................... 7,000,000 7,000,000 112,112 0
Hotel Union & Hotel Industry of
Hawaii........................ 290,000 290,000 4,644 0
ICI American Holdings Trust..... 1,730,000 1,730,000 27,707 0
Island Holdings................. 20,000 20,000 320 0
Jackson Investment Fund Ltd..... 2,000,000 2,000,000 32,032 0
Jeffries & Company Inc.......... 8,000 8,000 128 0
J.M. Hull Associates, L.P....... 250,000 250,000 4,004 0
J.P. Morgan Securities Inc...... 6,000,000 6,000,000 96,096 0
Julius Baer Securities.......... 675,000 675,000 10,810 0
J.W. McConnell Family
Foundation.................... 400,000 400,000 6,406 0
Kapiolani Health................ 50,000 50,000 800 0
Kapiolani Medical Center........ 400,000 400,000 6,406 0
Klesius, Michael and Judith..... 50,000 50,000 800 0
LDG Limited..................... 250,000 250,000 4,004 0
Lehman Brothers Inc............. 1,800,000 1,800,000 28,828 0
Lincoln National Convertible
Securities Fund............... 1,500,000 1,500,000 24,024 0
Lipper Convertibles L.P......... 2,000,000 2,000,000 32,032 0
Lipper Convertibles Series II,
L.P........................... 3,000,000 3,000,000 48,048 0
Lipper Offshore Convertibles,
L.P........................... 3,000,000 3,000,000 48,048 0
Mag & Co., as Nominee for
Fidelity Financial Trust:
Fidelity Convertible Securities
(1)........................... 11,000,000 11,000,000 176,176 0
MainStay Convertible Fund....... 3,000,000 3,000,000 48,048 500
Major League Baseball........... 2,700,000 2,700,000 43,243 0
Merrill Lynch Pierce Fenner and
Smith Inc..................... 1,372,000 1,372,000 21,973 0
MFS Convertible Securities
Fund.......................... 5,000 5,000 80 0
Minnesota Power Inc............. 2,000,000 2,000,000 32,032 0
</TABLE>
<PAGE>
<TABLE>
<CAPTION>
AMOUNT OF 7% AMOUNT OF 7% SHARES OF
DEBENTURES THAT DEBENTURES OWNED SHARES THAT COMMON STOCK OWNED
NAME MAY BE SOLD BEFORE OFFERING MAY BE SOLD BEFORE OFFERING
---- --------------- ---------------- ----------- ------------------
<S> <C> <C> <C> <C>
Morgan Stanley Dean Witter...... 41,005,000 41,005,000 656,736 0
Morgan Stanley Dean Witter
Convertible Securities
Trust......................... 1,000,000 1,000,000 16,016 0
Motion Picture Industry Health
Plan-Active Member Fund....... 645,000 645,000 10,330 0
Motion Picture Industry Health
Plan-Retiree Member Fund...... 330,000 330,000 5,285 0
Museum of Fine Arts, Boston..... 82,000 82,000 1,313 0
Nalco Chemical Company.......... 350,000 350,000 5,605 0
New Hampshire Retirement
System........................ 489,000 489,000 7,831 0
Nicholas Applegate Convertible
Fund.......................... 6,920,000 6,920,000 110,830 0
OCM Convertible Limited
Partnership................... 165,000 165,000 2,642 0
OCM Convertible Trust........... 2,910,000 2,910,000 46,606 0
Ohio Nat'l Fd, Inc. Capital
Apprec........................ 240,000 240,000 3,843 0
ONEX Industrial Partners
Limited....................... 350,000 350,000 5,605 0
Paloma Securities LLC........... 250,000 250,000 4,004 0
Parker-Hannifin Corporation..... 102,000 102,000 1,633 0
Paloma Strategic Securities
Limited....................... 250,000 250,000 4,004 0
Partner Reinsurance Company
Ltd........................... 640,000 640,000 10,250 0
Pebble Capital Inc.............. 142,000 142,000 2,274 0
Pell Rudman Trust Co., N.A...... 1,520,000 1,520,000 24,344 0
Penn Series Funds,
Inc.--Flexibility Managed Fund 1,625,000 1,625,000 26,026 0
Pepperdine University PoolA#1... 95,000 95,000 1,521 0
Physicians Life................. 640,000 640,000 10,250 0
ProMutual....................... 305,000 305,000 4,884 0
Putnam Balanced Retirement
Fund.......................... 231,000 231,000 3,699 0
Putnam Convertible Income-
Growth Trust.................. 5,154,000 5,154,000 82,546 0
Putnam Convertible Opportunities
and Income Trust.............. 236,000 236,000 3,779 0
Putnam High Income Convertible
and Bond Fund................. 750,000 750,000 12,012 0
Queens Health Plan.............. 80,000 80,000 1,281 0
Raytheon Company Master Pension
Trust......................... 2,660,000 2,660,000 42,602 0
Rhone-Poulenc Rorer Pension
Plan.......................... 83,000 83,000 1,329 0
Robertson Stephens.............. 2,000,000 2,000,000 21,649 0
Sage Capital.................... 1,600,000 1,600,000 25,625 0
Salomon Smith Barney............ 1,075,000 1,075,000 17,217 0
San Diego City Retirement....... 1,942,000 1,942,000 31,103 0
S.G. Cowen Securities
Corporation................... 3,000,000 3,000,000 48,048 0
San Diego County Convertible.... 5,649,000 5,649,000 90,474 0
Smith Barney Premium Total
Return Fund................... 10,000,000 10,000,000 160,160 0
Southern Farm Bureau Life
Insurance--FRIC............... 875,000 875,000 14,014 0
Starvest Combined Portfolio..... 250,000 250,000 4,004 0
Starvest Managed Portfolio...... 145,000 145,000 2,322 0
</TABLE>
<PAGE>
<TABLE>
<CAPTION>
AMOUNT OF 7% AMOUNT OF 7% SHARES OF
DEBENTURES THAT DEBENTURES OWNED SHARES THAT COMMON STOCK OWNED
NAME MAY BE SOLD BEFORE OFFERING MAY BE SOLD BEFORE OFFERING
---- --------------- ---------------- ----------- ------------------
<S> <C> <C> <C> <C>
State Employees' Retirement Fund
of the State of Delaware...... 1,985,000 1,985,000 31,791 0
State of Connecticut Combined
Investment Funds.............. 6,810,000 6,810,000 109,069 0
State of Oregon Equity.......... 7,875,000 7,875,000 126,126 0
Summers Hill Global Partners
L.P........................... 125,000 125,000 2,002 0
Taunus Enterprises Ltd.......... 300,000 300,000 4,804 0
The Guardian Life Insurance
Company of America............ 10,800,000 10,800,000 172,972 0
The Guardian Pension Trust...... 600,000 600,000 9,609 0
The Shelby Fund................. 500,000 500,000 8,008 0
TQA Arbitrage Fund, L.P......... 1,150,000 1,150,000 18,418 0
TQA Leverage Fund, L.P.......... 1,800,000 1,800,000 28,828 0
TQA Vantage Fund, Ltd........... 4,200,000 4,200,000 67,267 0
TQA Vantage Plus Fund, Ltd...... 500,000 500,000 8,008 0
The TCW Group, Inc.............. 29,750,000 29,750,000 476,476 0
Tracor Inc., Employee Retirement
Plan.......................... 145,000 145,000 2,322 0
Transamerica Insurance
Corporation of California..... 3,000,000 3,000,000 48,048 0
Transamerica Life Insurance &
Annuity Company............... 12,000,000 12,000,000 192,192 0
University of Rochester......... 78,000 78,000 1,249 0
Vanguard Convertible Securities
Fund, Inc..................... 4,020,000 4,020,000 64,384 0
Viacom Pension Plan Master
Trust......................... 50,000 50,000 800 0
Wake Forest University.......... 1,515,000 1,515,000 24,264 0
Zeneca Holdings Trust........... 1,390,000 1,390,000 22,262 0
</TABLE>
------------------------
(1) The entity is either an investment company or portfolio of an investment
company registered under Section 8 of the Investment Company Act of 1940, as
amended, or a private investment account advised by Fidelity Management &
Research Company, or FMR Co. FMR Co. is a Massachusetts corporation and an
investment advisor registered under Section 203 of the Investment Advisers
Act of 1940, as amended, and provides investment industry advisory services
to each of the Fidelity entities identified above, and to other registered
investment companies and to certain other funds which are generally offered
to a limited group of investors. FMR Co. owns 10.34% of Sepracor's
outstanding common stock. FMR Co. is a wholly owned subsidiary of FMR Corp.,
a Massachusetts corporation.
The date of this Prospectus Supplement is October 30, 2000.
