<SEC-DOCUMENT>0001104659-18-018390.txt : 20180316
<SEC-HEADER>0001104659-18-018390.hdr.sgml : 20180316
<ACCEPTANCE-DATETIME>20180316181930
ACCESSION NUMBER:		0001104659-18-018390
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		2
CONFORMED PERIOD OF REPORT:	20180315
FILED AS OF DATE:		20180316
DATE AS OF CHANGE:		20180316

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			PRINS RICHARD K
		CENTRAL INDEX KEY:			0001047579

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36509
		FILM NUMBER:		18696983

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
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>a4.xml
<DESCRIPTION>4
<TEXT>
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<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-03-15</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001047579</rptOwnerCik>
            <rptOwnerName>PRINS RICHARD K</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>2018-03-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>16598</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.66</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>45442</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2018-03-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>16598</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>19.9011</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>28844</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>14.66</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-03-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>16598</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2018-12-20</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>16598</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $19.77 to $20.18, 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 sold at each separate price.</footnote>
        <footnote id="F2">Shares subject to the option are fully vested and immediately exercisable.</footnote>
    </footnotes>

    <remarks>Exhibit 24 - Power of Attorney</remarks>

    <ownerSignature>
        <signatureName>/s/ William Peters, by power of attorney</signatureName>
        <signatureDate>2018-03-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</DOCUMENT>
<DOCUMENT>
<TYPE>EX-24
<SEQUENCE>2
<FILENAME>ex-24.htm
<DESCRIPTION>EX-24
<TEXT>


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<p align="right" style="margin:0in 0in .0001pt;text-align:right;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">Exhibit&nbsp;24<a name="Exhibit24_110114"></a></font></b></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><b><font size="2" face="Times New Roman" style="font-size:10.0pt;font-weight:bold;">POWER OF ATTORNEY</font></b></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">The undersigned, as a Section&nbsp;16 reporting person of Amphastar Pharmaceuticals,&nbsp;Inc., (the &#147;Company&#148;), hereby constitutes and appoints Jason Shandell, William Peters and Eva Wen, and each of them, as the undersigned&#146;s true and lawful attorney-in-fact to:</font></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="font-size:10.0pt;margin:0in 0in .0001pt 1.0in;text-indent:-.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">1.</font><font size="1" style="font-size:3.0pt;">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; </font>prepare, execute in the undersigned&#146;s name and on the undersigned&#146;s behalf, and submit to the Securities and Exchange Commission (the &#147;SEC&#148;) a Form&nbsp;ID, including amendments thereto, and any other documents necessary or appropriate to obtain EDGAR codes and passwords enabling the undersigned to make electronic filings with the SEC of reports required by Section&nbsp;16(a)&nbsp;of the Securities Exchange Act of 1934 or any rule&nbsp;or regulation of the SEC;</p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="font-size:10.0pt;margin:0in 0in .0001pt 1.0in;text-indent:-.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">2.</font><font size="1" style="font-size:3.0pt;">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; </font>complete and execute Forms 4 and 5 and other forms and all amendments thereto as such attorney-in-fact shall in his discretion determine to be required or advisable pursuant to Section&nbsp;16 of the Securities Exchange Act of 1934 (as amended) and the rules&nbsp;and regulations promulgated thereunder, or any successor laws and regulations, as a consequence of the undersigned&#146;s ownership, acquisition or disposition of securities of the Company; and</p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="font-size:10.0pt;margin:0in 0in .0001pt 1.0in;text-indent:-.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">3.</font><font size="1" style="font-size:3.0pt;">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; </font>do all acts necessary in order to file such forms with the SEC, any securities exchange or national association, the Company and such other person or agency as the attorneys-in-fact shall deem appropriate.</p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">The undersigned hereby ratifies and confirms all that said attorneys-in-fact and agents shall do or cause to be done by virtue hereof.&#160; The undersigned acknowledges that the foregoing attorneys-in-fact, in serving in such capacity at the request of the undersigned, are not assuming, nor is the Company assuming, any of the undersigned&#146;s responsibilities to comply with Section&nbsp;16 of the Securities Exchange Act of 1934 (as amended).</font></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">This Power of Attorney shall remain in full force and effect until the undersigned is no longer required to file Forms 4 and 5 with respect to the undersigned&#146;s holdings of and transactions in securities issued by the Company, unless earlier revoked by the undersigned in a signed writing delivered to the Company and the foregoing attorneys-in-fact.</font></p>
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<p style="font-size:10.0pt;margin:0in 0in .0001pt;text-indent:.5in;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of this 15</font><font size="1" style="font-size:6.5pt;position:relative;top:-3.0pt;">th</font>&#160;day of March, 2018.</p>
<p align="center" style="margin:0in 0in .0001pt;text-align:center;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
<table border="0" cellspacing="0" cellpadding="0" width="100%" style="border-collapse:collapse;">
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<td width="50%" valign="top" style="padding:0in 0in 0in 0in;width:50.0%;">
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="9%" valign="top" style="padding:0in 0in 0in 0in;width:9.16%;">
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Signature:</font></p>    </td>
<td width="40%" colspan="2" valign="top" style="border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 0in 0in;width:40.84%;">
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">/s/ Richard Prins</font></p>    </td>   </tr>
<tr>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>    </td>
<td width="10%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:10.0%;">
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>    </td>
<td width="40%" valign="top" style="padding:0in 0in 0in 0in;width:40.0%;">
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>    </td>   </tr>
<tr>
<td width="50%" valign="top" style="padding:0in 0in 0in 0in;width:50.0%;">
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:1.0pt;">&nbsp;</font></p>    </td>
<td width="10%" colspan="2" valign="top" style="padding:0in 0in 0in 0in;width:10.0%;">
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Print Name:</font></p>    </td>
<td width="40%" valign="top" style="border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 0in 0in;width:40.0%;">
<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">Richard Prins</font></p>    </td>   </tr>
<tr height="0">
<td width="354" style="border:none;"></td>
<td width="65" style="border:none;"></td>
<td width="6" style="border:none;"></td>
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<p style="margin:0in 0in .0001pt;"><font size="2" face="Times New Roman" style="font-size:10.0pt;">&nbsp;</font></p>
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