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RxNorm is the NLM's normalized naming system for clinical drugs and dose forms. It collapses brand variants, packaging differences, and source-vocabulary noise into a single, stable identifier (RxCUI) per concept, with explicit links to ingredients, brands, and clinical drug forms.

An RxCUI is the persistent ID for a single RxNorm concept. The same RxCUI keeps pointing at the same drug concept release after release, even when names or sources change. That stability is what makes RxNorm useful for medication reconciliation and analytics.

NDC codes describe a specific package SKU at a specific manufacturer. RxNorm describes the clinically relevant drug. One RxCUI can map to dozens of NDCs (different manufacturers, different package sizes), and we list those NDC mappings on each concept page.

RxNorm concepts carry direct links to UMLS CUIs and SNOMED CT product codes when available. Through the UMLS bridge they can also reach ICD-10 codes (for instance, for indication-based coding) and LOINC observations. Our API exposes all of this on the cross_references field.

Browsing concepts is free. Programmatic access at /v1/reference/rxnorm/* requires an API key. RxNorm itself is in the public domain, so there is no upstream license fee, but our bandwidth and uptime are not.

RxNorm releases monthly. We rebuild within a few business days of each release, and the concept-id history is preserved so previous lookups continue to resolve.