This code system http://terminology.hl7.org/CodeSystem/standardBillingUnit defines many codes, but they are not represented here

 <status value="active"/> <experimental value="false"/> <date value="2019-03-20T00:00:00-04:00"/> <publisher value="TBD - External Body"/> <contact> <name value="National Council for Prescription Drug Programs (NCPDP),National Council for Prescription Drug Progr"/> </contact> <description value="NCPDP standard product billing codes of NCPDP field Unit of Measure (600-28). This billing code is assigned per product, placed in the Structured Product Label, and used in the pharmacy billing processing for consistent billing unit."/> <caseSensitive value="true"/> <content value="not-present"/> </CodeSystem>