This is the CodeSystem that contains all the codes in PMIX Opioid Treatment Code (http://terminology.hl7.org/CodeSystem/PMIXOpioidTreatmentCode) and PMIX Opioid Treatment Code (http://terminology.hl7.org/CodeSystem/PMIXOpioidTreatmentCode). E.g. what you have to deal with if you get resources containing codes in either of them