content: <?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
    <headerData>
      <submissionType>144</submissionType>
      <filerInfo>
        <filer>
          <filerCredentials>
            <cik>0001866024</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
  
      </filerInfo>
    </headerData>
    <formData>
      <issuerInfo>
        <issuerCik>0001297184</issuerCik>
        <issuerName>Amphastar Pharmaceuticals</issuerName>
        <secFileNumber>001-36509</secFileNumber>
        <issuerAddress>
          <com:street1>11570 Sixth Street</com:street1>
          <com:city>Rancho Cucamonga</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>91730</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>909-942-4211</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>Gayle Deflin</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Board Member</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>UBS Financial Services 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>1500</noOfUnitsSold>
        <aggregateMarketValue>64727.7</aggregateMarketValue>
        <noOfUnitsOutstanding>48274000</noOfUnitsOutstanding>
        <approxSaleDate>05/15/2023</approxSaleDate>
        <securitiesExchangeName>NASD</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>06/07/2022</acquiredDate>
        <natureOfAcquisitionTransaction>RSU Vesting</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Gayle Deflin</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>6019</amountOfSecuritiesAcquired>
        <paymentDate>05/15/2023</paymentDate>
        <natureOfPayment>NA</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <noticeSignature>
        <noticeDate>05/16/2023</noticeDate>
        <signature>/s/ UBS Financial Services Inc, as attorney-in-fact for Gayle Deflin</signature>
      </noticeSignature>
    </formData>
  </edgarSubmission>
metadata_documents: [{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 2806}]
text: 144
  0001866024
  XXXXXXXX
  LIVE
  0001297184
  Amphastar Pharmaceuticals
  001-36509
  11570 Sixth Street
  Rancho Cucamonga
  CA
  91730
  909-942-4211
  Gayle Deflin
  Board Member
  Common
  UBS Financial Services Inc
  1000 Harbor Blvd
  3rd Floor
  Weehawken
  NJ
  07086
  1500
  64727.7
  48274000
  05/15/2023
  NASD
  Common
  06/07/2022
  RSU Vesting
  Gayle Deflin
  N
  6019
  05/15/2023
  NA
  Y
  05/16/2023
  /s/ UBS Financial Services Inc, as attorney-in-fact for Gayle Deflin