Final answer:
The National Library of Medicine (NLM) is the entity responsible for maintaining RxNorm, which is a nomenclature for clinical drugs used in health informatics.
Step-by-step explanation:
The organization responsible for the maintenance of RxNorm is the National Library of Medicine (NLM). RxNorm is a standardized nomenclature for clinical drugs and is used for electronic prescribing and the exchange of drug information across systems. It delivers normalized naming and coding for medications and serves as an important tool for pharmacies, hospitals, and other institutions in the health informatics field.