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

    <schemaVersion>X0202</schemaVersion>

    <documentType>5</documentType>

    <periodOfReport>2005-12-31</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <form3HoldingsReported>0</form3HoldingsReported>

    <form4TransactionsReported>0</form4TransactionsReported>

    <issuer>
        <issuerCik>0001106773</issuerCik>
        <issuerName>FIRST HORIZON PHARMACEUTICAL CORP</issuerName>
        <issuerTradingSymbol>FHRX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001033150</rptOwnerCik>
            <rptOwnerName>KAPOOR JOHN N</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O FIRST HORIZON PHARMACEUTICAL CORP.</rptOwnerStreet1>
            <rptOwnerStreet2>6195 SHILOH ROAD</rptOwnerStreet2>
            <rptOwnerCity>ALPHARETTA</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>30005</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2005-04-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>358583</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>17.099</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <valueOwnedFollowingTransaction>
                    <value>7406374</value>
                </valueOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On April 21, 2005, Dr. Kapoor was appointed Trustee of the Bob Kapoor 2000 Trust, dated April 10, 2000, thereby replacing Bank of America, N.A., as Trustee.  As Trustee, Dr. Kapoor has investment and voting power over the Issuer's 358,583 shares in the Trust.  Bob Kapoor, Dr. Kapoor's brother, is the grantor of the Trust and a Trust beneficiary.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ John N. Kapoor</signatureName>
        <signatureDate>2006-02-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
