<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-12-03</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001059790</issuerCik>
        <issuerName>POZEN INC /NC</issuerName>
        <issuerTradingSymbol>POZN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001135011</rptOwnerCik>
            <rptOwnerName>PLACHETKA JOHN R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O POZEN INC.</rptOwnerStreet1>
            <rptOwnerStreet2>1414 RALEIGH ROAD, SUITE 400</rptOwnerStreet2>
            <rptOwnerCity>CHAPEL HILL</rptOwnerCity>
            <rptOwnerState>NC</rptOwnerState>
            <rptOwnerZipCode>27517</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>506799</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-12-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>23479</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.136</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1232623</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>218910</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1157808</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Silver Hill Investments, LLC</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>22631</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F6"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Stock option exercise and open market sales pursuant to a 10b5-1 trading plan adopted by the Reporting Person in accordance with rule 10b5-1 of the Securities Exchange Act of 1934, as amended.</footnote>
        <footnote id="F2">The price in column 4 is a weighted average price. The prices actually received by the reporting person in this transaction range from $8.07 to $8.175.</footnote>
        <footnote id="F3">Beneficially owned by John R. Plachetka, indirectly, through the Revocable Declaration Trust u/a 1/31/2000, John R. Plachetka, Trustee.</footnote>
        <footnote id="F4">Beneficially owned by John R. Plachetka, indirectly, through the Revocable Declaration Trust u/a 1/31/2000, Clare A. Plachetka, Trustee.</footnote>
        <footnote id="F5">Beneficially owned by John R. Plachetka, indirectly, as manager of Silver Hill Investments, LLC. Silver Hill Investments LLC is 50% owned by the Family Trust under the John R. Plachetka Irrevocable Trust dated 4/20/2000, Wachovia Bank N.A. and Clare A. Plachetka, Trustees (the &quot;Family Trust&quot;); 40% owned by the Revocable Declaration of Trust u/a 1/31/2000, John R. Plachetka, Trustee; and 10% owned by the Revocable Declaration of Trust u/a 1/31/2000, Clare A. Plachetka, Trustee.</footnote>
        <footnote id="F6">Beneficially owned by John R. Plachetka, indirectly, through the Family Trust. The shares in the Family Trust are held in trust for the benefit of Clare A. Plachetka and John R. and Clare A. Plachetka's children.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ John E. Barnhardt, Attorney-in-fact</signatureName>
        <signatureDate>2015-12-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
