Union of http://www.nlm.nih.gov/research/umls/rxnorm and http://www.nlm.nih.gov/research/umls/rxnorm

This is the CodeSystem that contains all the codes in RxNorm (http://www.nlm.nih.gov/research/umls/rxnorm) and RxNorm (http://www.nlm.nih.gov/research/umls/rxnorm). E.g. what you have to deal with if you get resources containing codes in either of them

CodeSystem

Generated Narrative: CodeSystem 2023f8dc-2ca7-4cc8-b1b8-b801585b8ec6-3548

This code system http://hl7.org/fhir/comparison/CodeSystem/2023f8dc-2ca7-4cc8-b1b8-b801585b8ec6-3548 defines codes, but no codes are represented here

Code