-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 Aqt2wZI9ijouTwXX5q4/vPaoKH6c3riy0FIBrdq3f7soeHYIFRTnOZtN3cFWrWQh
 dGOv2k8jNqnhc9mIuS09Qg==

<SEC-DOCUMENT>0001251553-05-000001.txt : 20050228
<SEC-HEADER>0001251553-05-000001.hdr.sgml : 20050228
<ACCEPTANCE-DATETIME>20050228153938
ACCESSION NUMBER:		0001251553-05-000001
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050228
FILED AS OF DATE:		20050228
DATE AS OF CHANGE:		20050228

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			SOUTHWELL DAVID P
		CENTRAL INDEX KEY:			0001251553

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-19410
		FILM NUMBER:		05645381

	MAIL ADDRESS:	
		STREET 1:		350 MAIN ST
		CITY:			CONCORD
		STATE:			MA
		ZIP:			01742

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SEPRACOR INC /DE/
		CENTRAL INDEX KEY:			0000877357
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				222536587
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		84 WATERFORD DRIVE
		CITY:			MARLBOROUGH
		STATE:			MA
		ZIP:			01757
		BUSINESS PHONE:		5084816700

	MAIL ADDRESS:	
		STREET 1:		84 WATERFORD DRIVE
		CITY:			MARLBOROUGH
		STATE:			MA
		ZIP:			01752
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-02-28</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000877357</issuerCik>
        <issuerName>SEPRACOR INC /DE/</issuerName>
        <issuerTradingSymbol>SEPR</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001251553</rptOwnerCik>
            <rptOwnerName>SOUTHWELL DAVID P</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>350 MAIN ST</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CONCORD</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01742</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Financial Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Sepracor Common Stock Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>64.5</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-02-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>100000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>64.5</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2006-02-24</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-02-23</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Sepracor Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>670998</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">20,000 options become exercisable on 2/24/2006
20,000 options become exercisable on 2/24/2007
20,000 options become exercisable on 2/24/2008
20,000 options become exercisable on 2/24/2009
20,000 options become exercisable on 2/24/2010</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Robyn McLaren, by power of attorney</signatureName>
        <signatureDate>2005-02-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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