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        <liveTestFlag>LIVE</liveTestFlag>
  
  
  
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        <issuerCik>0001297184</issuerCik>
        <issuerName>Amphastar Pharmaceuticals, Inc.</issuerName>
        <secFileNumber>001-36509</secFileNumber>
        <issuerAddress>
          <com:street1>11570 6th Street</com:street1>
          <com:city>Rancho Cucamonga</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>91730</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>9099809484</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>William Peters</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Officer</relationshipToIssuer>
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        <securitiesClassTitle>Common</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>UBS Financial Servcies Inc</name>
          <address>
            <com:street1>1000 Harbor Blvd.</com:street1>
            <com:street2>3rd Floor</com:street2>
            <com:city>Weehawken </com:city>
            <com:stateOrCountry>NJ</com:stateOrCountry>
            <com:zipCode>07086</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>10500</noOfUnitsSold>
        <aggregateMarketValue>414750</aggregateMarketValue>
        <noOfUnitsOutstanding>47896820</noOfUnitsOutstanding>
        <approxSaleDate>04/13/2023</approxSaleDate>
        <securitiesExchangeName>NASDAQ</securitiesExchangeName>
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        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>04/13/2023</acquiredDate>
        <natureOfAcquisitionTransaction>Exercise of Stock Options</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>10500</amountOfSecuritiesAcquired>
        <paymentDate>04/13/2023</paymentDate>
        <natureOfPayment>CASH</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
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          <address>
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            <com:city>Rancho Cucamonga</com:city>
            <com:stateOrCountry>CA</com:stateOrCountry>
            <com:zipCode>91730</com:zipCode>
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        <securitiesClassTitle>COMMON</securitiesClassTitle>
        <saleDate>03/01/2023</saleDate>
        <amountOfSecuritiesSold>10874</amountOfSecuritiesSold>
        <grossProceeds>398685</grossProceeds>
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          <address>
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            <com:city>Rancho Cucamonga</com:city>
            <com:stateOrCountry>CA</com:stateOrCountry>
            <com:zipCode>91730</com:zipCode>
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        <securitiesClassTitle>COMMON</securitiesClassTitle>
        <saleDate>03/15/2023</saleDate>
        <amountOfSecuritiesSold>12776</amountOfSecuritiesSold>
        <grossProceeds>465473</grossProceeds>
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            <com:zipCode>91730</com:zipCode>
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        </sellerDetails>
        <securitiesClassTitle>COMMON</securitiesClassTitle>
        <saleDate>04/10/2023</saleDate>
        <amountOfSecuritiesSold>10032</amountOfSecuritiesSold>
        <grossProceeds>404792</grossProceeds>
      </securitiesSoldInPast3Months>
      <noticeSignature>
        <noticeDate>04/13/2023</noticeDate>
        <planAdoptionDates>
          <planAdoptionDate>05/18/2022</planAdoptionDate>
        </planAdoptionDates>
        <signature>/s/ UBS Financial Services Inc, as attorney-in-fact for William Peters</signature>
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text: 144
  0001263136
  XXXXXXXX
  LIVE
  0001297184
  Amphastar Pharmaceuticals, Inc.
  001-36509
  11570 6th Street
  Rancho Cucamonga
  CA
  91730
  9099809484
  William Peters
  Officer
  Common
  UBS Financial Servcies Inc
  1000 Harbor Blvd.
  3rd Floor
  Weehawken
  NJ
  07086
  10500
  414750
  47896820
  04/13/2023
  NASDAQ
  Common
  04/13/2023
  Exercise of Stock Options
  Issuer
  N
  10500
  04/13/2023
  CASH
  N
  William Peters
  11570 6th Street
  Rancho Cucamonga
  CA
  91730
  COMMON
  03/01/2023
  10874
  398685
  William Peters
  11570 6th Street
  Rancho Cucamonga
  CA
  91730
  COMMON
  03/15/2023
  12776
  465473
  William Peters
  11570 6th Street
  Rancho Cucamonga
  CA
  91730
  COMMON
  04/10/2023
  10032
  404792
  04/13/2023
  05/18/2022
  /s/ UBS Financial Services Inc, as attorney-in-fact for William Peters