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Unified Medical Language System® (UMLS®)

National Drug File - Reference Terminology Source Information

The National Drug File - Reference Terminology (NDF-RT) is produced by the U.S. Department of Veterans Affairs, Veterans Health Administration (VHA).

NDF-RT is an extension of the VHA National Drug File (NDF). It organizes the drug list into a formal representation.

NDF-RT is used for modeling drug characteristics including ingredients, chemical structure, dose form, physiologic effect, mechanism of action, pharmacokinetics, and related diseases.

NDF-RT combines the NDF hierarchical drug classification with a multi-category reference model. The categories are:

  1. Cellular or Molecular Interactions [MoA]
  2. Chemical Ingredients [Chemical/Ingredient]
  3. Clinical Kinetics [PK]
  4. Diseases, Manifestations or Physiologic States [Disease/Finding]
  5. Dose Forms [Dose Form]
  6. Pharmaceutical Preparations
  7. Physiological Effects [PE]
  8. Therapeutic Categories [TC]
  9. VA Drug Interactions [VA Drug Interaction]

For more information about NDF in the Metathesaurus, see the NDF source synopsis.

Update Frequency
NDF-RT is updated monthly.

Metathesaurus Update Frequency
NDF-RT is updated in each Metathesaurus release as part of RxNorm.

Sites Consulted

  1. Carter JS, Brown SH, Bauer BA, Elkin PL, Erlbaum MS, Froehling DA, Lincoln MJ, Rosenbloom ST, Wahner-Roedler DL, Tuttle MS. Categorical information in pharmaceutical terminologies. AMIA Annu Symp Proc. 2006:116-20. Cited in: PubMed; PMID 17238314. Available from:
  2. Chute CG, Carter JS, Tuttle MS, Haber M, Brown SH. Integrating pharmacokinetics knowledge into a drug ontology: as an extension to support pharmacogenomics. AMIA Annu Symp Proc. 2003:170-4. Cited in PubMed; PMID: 14728156. About the HGNC; [updated 2007 Feb 16; cited 2008 Sep 17]. Available from:

Last Reviewed: May 8, 2017