This is the ValueSet that contains all the codes in ModifyPrescriptionReasonType (http://terminology.hl7.org/ValueSet/v3-ModifyPrescriptionReasonType) and ModifyPrescriptionReasonType (http://terminology.hl7.org/ValueSet/v3-ModifyPrescriptionReasonType). E.g. what you have to deal with if you get resources containing codes in either of them