<SEC-DOCUMENT>0001104659-14-063354.txt : 20140827
<SEC-HEADER>0001104659-14-063354.hdr.sgml : 20140827
<ACCEPTANCE-DATETIME>20140827135715
ACCESSION NUMBER:		0001104659-14-063354
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20140825
FILED AS OF DATE:		20140827
DATE AS OF CHANGE:		20140827

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:			Lee Howard
		CENTRAL INDEX KEY:			0001379941

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36509
		FILM NUMBER:		141067842

	MAIL ADDRESS:	
		STREET 1:		13F-2, NO. 36, LANE 48, SECTION 3
		STREET 2:		NAN-JING EAST ROAD
		CITY:			TAIPEI, TAIWAN
		STATE:			F4
		ZIP:			00000
</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>2014-08-25</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001379941</rptOwnerCik>
            <rptOwnerName>Lee Howard</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>2014-08-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>6000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>10.837</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>101215</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The price reported in Column 4 is a weighted average price. These shares were acquired in multiple transactions at prices ranging from $10.15 to $11.57, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares acquired at each separate price within the ranges set forth in this footnote.</footnote>
        <footnote id="F2">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/ Richard Whitlow as Attorney-in-Fact for Howard Lee</signatureName>
        <signatureDate>2014-08-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
