Analyzing categorical information in two publicly available drug terminologies: RxNorm and NDF-RT

J Am Med Inform Assoc. Jul-Aug 2010;17(4):432-9. doi: 10.1136/jamia.2009.001289.


Background: The RxNorm and NDF-RT (National Drug File Reference Terminology) are a suite of terminology standards for clinical drugs designated for use in the US federal government systems for electronic exchange of clinical health information. Analyzing how different drug products described in these terminologies are categorized into drug classes will help in their better organization and classification of pharmaceutical information.

Methods: Mappings between drug products in RxNorm and NDF-RT drug classes were extracted. Mappings were also extracted between drug products in RxNorm to five high-level NDF-RT categories: Chemical Structure; cellular or subcellular Mechanism of Action; organ-level or system-level Physiologic Effect; Therapeutic Intent; and Pharmacokinetics. Coverage for the mappings and the gaps were evaluated and analyzed algorithmically.

Results: Approximately 54% of RxNorm drug products (Semantic Clinical Drugs) were found not to have a correspondence in NDF-RT. Similarly, approximately 45% of drug products in NDF-RT are missing from RxNorm, most of which can be attributed to differences in dosage, strength, and route form. Approximately 81% of Chemical Structure classes, 42% of Mechanism of Action classes, 75% of Physiologic Effect classes, 76% of Therapeutic Intent classes, and 88% of Pharmacokinetics classes were also found not to have any RxNorm drug products classified under them. Finally, various issues regarding inconsistent mappings between drug concepts were identified in both terminologies.

Conclusion: This investigation identified potential limitations of the existing classification systems and various issues in specification of correspondences between the concepts in RxNorm and NDF-RT. These proposals and methods provide the preliminary steps in addressing some of the requirements.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Databases, Factual
  • Drug Information Services*
  • Humans
  • Information Storage and Retrieval
  • Medical Record Linkage*
  • Medication Systems*
  • National Library of Medicine (U.S.)
  • Pharmaceutical Preparations / classification*
  • Reference Standards
  • Terminology as Topic*
  • United States
  • United States Department of Veterans Affairs
  • Vocabulary, Controlled*


  • Pharmaceutical Preparations