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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-11-13</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>
                <footnoteId id="F1"/>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>46782</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-11-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>150000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>7.001</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1404102</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>221910</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F5"/>
                </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="F6"/>
                </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="F7"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Shares underlying restricted stock units.</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 $7.00 to $7.20.</footnote>
        <footnote id="F3">The reporting person has provided to the issuer, and the issuer will provide to any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range reported.</footnote>
        <footnote id="F4">Beneficially owned by John R. Plachetka, indirectly, through the Revocable Declaration Trust u/a 1/31/2000, John R. Plachetka, Trustee.</footnote>
        <footnote id="F5">Beneficially owned by John R. Plachetka, indirectly, through the Revocable Declaration Trust u/a 1/31/2000, Clare A. Plachetka, Trustee.</footnote>
        <footnote id="F6">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="F7">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>2015-11-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
