<SEC-DOCUMENT>0001104659-14-062252.txt : 20140820
<SEC-HEADER>0001104659-14-062252.hdr.sgml : 20140820
<ACCEPTANCE-DATETIME>20140820160212
ACCESSION NUMBER:		0001104659-14-062252
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20140819
FILED AS OF DATE:		20140820
DATE AS OF CHANGE:		20140820

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Amphastar Pharmaceuticals, Inc.
		CENTRAL INDEX KEY:			0001297184
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				330702205
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		11570 SIXTH STREET
		CITY:			RANCHO CUCAMONGA
		STATE:			CA
		ZIP:			91730
		BUSINESS PHONE:		909-980-9484

	MAIL ADDRESS:	
		STREET 1:		11570 SIXTH STREET
		CITY:			RANCHO CUCAMONGA
		STATE:			CA
		ZIP:			91730

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			ZASLOFF MICHAEL A
		CENTRAL INDEX KEY:			0001033511
		STATE OF INCORPORATION:			PA
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36509
		FILM NUMBER:		141054935
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>a4.xml
<DESCRIPTION>4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2014-08-19</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001297184</issuerCik>
        <issuerName>Amphastar Pharmaceuticals, Inc.</issuerName>
        <issuerTradingSymbol>AMPH</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001033511</rptOwnerCik>
            <rptOwnerName>ZASLOFF MICHAEL A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O AMPHASTAR PHARMACEUTICALS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>11570 6TH STREET</rptOwnerStreet2>
            <rptOwnerCity>RANCHO CUCAMONGA</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>91730</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2014-08-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>3500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>9.9999</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>17639</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">This includes 5,457 shares underlying deferred stock units that were granted on 12/20/2013 and fully vest on the first anniversary of the grant date. Such shares were previously reported on a separate line on the Reporting Person's Form 3 filed 6/24/14 but are now consolidated with the Reporting Person's other direct holdings for convenience.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Ken Stupak as Attorney-in-Fact for Michael A. Zasloff</signatureName>
        <signatureDate>2014-08-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
