RxNorm

Key facts

Produced by

National Library of Medicine (NLM)

Identifier

RxNorm Concept Unique Identifier (RxCUI)

Release cycle

Full monthly release, plus weekly updates

Scope

Prescription and many over-the-counter drugs available in the United States

Access

Full files need a free UMLS license; a prescribable subset needs none

What is RxNorm?

Drug databases, pharmacy systems and electronic health records (EHRs) describe the same medicine in many different ways. RxNorm, produced by the National Library of Medicine (NLM), gives each clinical drug a normalized name and a concept identifier, the RxCUI, and links the names and codes that other sources use for that drug.

A normalized name follows a fixed pattern of ingredient, strength and dose form, plus the brand name for branded drugs, for example "metformin hydrochloride 500 MG Oral Tablet." RxNorm draws on sources including commercial drug knowledge bases, FDA structured product labeling and the Department of Veterans Affairs, and it records National Drug Codes (NDCs) as attributes of the concepts they belong to.

How RxNorm is structured

Each RxCUI has a term type (TTY) that marks its level of detail, and relationships connect the levels:

NLM also offers RxNav and the RxNorm API for looking up and navigating these relationships without loading the full files.

• IN (ingredient): the active ingredient, such as atorvastatin.
• BN (brand name): a proprietary name, such as Lipitor.
• SCD (semantic clinical drug): ingredient, strength and dose form for a generic.
• SBD (semantic branded drug): an SCD plus the brand name.
• GPCK and BPCK: generic and branded packs, such as dose packs that combine several drugs.

Why RxNorm matters

RxNorm is the bridge between package-level drug codes and clinical drug concepts:

• Joining drug data: mapping NDCs to RxCUIs rolls many package-level codes up to one clinical drug or ingredient.
• Interoperability: federal health IT certification and the United States Core Data for Interoperability (USCDI) name RxNorm for medications, so EHR medication lists and e-prescriptions usually carry RxCUIs.
• Medicare Part D: CMS formulary files identify drugs by RxCUI, so formulary coverage analysis starts from RxNorm.
• Normalization: grouping by ingredient or brand name makes it possible to count a molecule across strengths, forms and labelers.

Limitations of RxNorm mappings

NDC-to-RxCUI links depend on source data and are not always complete, especially for older, repackaged or discontinued NDCs. RxCUIs can also be retired or merged over time, so historical datasets should be checked against RxNorm history information before joining.