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RxNorm provides standard names for clinical drugs (active ingredient + strength + dose form) and for dose forms as administered to a patient. RxNorm is a standardized nomenclature of the Unified Medical Language System (UMLS) for clinical drugs and drug delivery devices.


RxNorm provides links from clinical drugs to their active ingredients, drug components, and related brand names. NDCs (National Drug Codes) for specific drug products are linked to that product in RxNorm. RxNorm links its names to drug vocabularies commonly used in pharmacy and drug interaction software, including First Databank, Micromedex, MediSpan, and Multum. RxNorm links vocabularies and mediates messages between systems not using the same vocabulary.

Evaluation of RxNorm

Classifying drug information and concepts has proven to be difficult for many reasons: drugs change frequently, so it is difficult to maintain the classification. It is difficult to decide where a pharmaceutical terminology ends and a knowledge base begins. James Cimino designed a desiderata to outline the requirements of a controlled vocabulary.

An evaluation of RxNorm based on Cimino’s criteria is shown below:


  • Keeping the content of the vocabulary current as new words and concepts are created and discovered.
  • RxNorm is intended to cover all prescription medications approved for human use in the United States. Prescription medications from other countries may be included as opportunities allow, a principal consideration being that there be an authoritative source of information about these drugs. Over-the-counter (OTC) medications will be added and covered, as well, when reliable information about the medications can be found.

Concept orientation

  • The terms must correspond with at least one meaning and no more than one meaning. Meanings correspond to no more than one term.
  • An RxNorm name should exist for every strength and dose of every available combination of clinically significant ingredients. Each term has one and only one meaning.

Concept permanence

  • Once created, the meaning of a concept never changes, even if the word is archived.
  • When a name had been used in a previous version of that source’s vocabulary but is not found in the most recent version—the old clinical drug records are given the term type OCD (for obsolete clinical drug. The record is updated with RxNorm as the source, but retains the original meaning . Any relationship to RxNorm records will be maintained.

Nonsemantic concept identifier

  • If each term in the vocabulary is to be associated with a concept, the concept must have a unique identifier.
  • Each concept (term) in RxNorm has a unique name.


  • Offer different hierarchical structures for different users.
  • RxNorm is structured in a single hierarchical format.

Formal definitions

  • Definitions are expresses in relationship to other concepts in the vocabulary.
  • Within RxNorm, generic and branded normalized forms are related to each other and to the names of their individual components by a well-defined set of named relationships.

Reject “not elsewhere classified”

  • Avoid this catch-phrase, which indicates the concept is not identified anywhere in the vocabulary.
  • RxNorm does not use ‘not elsewhere classified’ as a classification.

Multiple granularities

  • Various levels of specificity are required for various types of users of the vocabulary.
  • RxNorm represents drugs at the granularity level used in clinical practice

Multiple consistent views - Multiple views of the vocabulary must be provided for different uses of the vocabulary.

  • Users can search RxNorm using different key words and concepts to allow different views of the terminology,

Evolve gracefully

  • The vocabulary must change with time.
  • Additions to the vocabulary will be added as new drugs are introduced into the market. RxNorm is available as a full update on a monthly basis.

Recognize redundancy

  • Avoid the condition where the same information is stated in two different ways.
  • Redundant terms and concepts are not used in RxNorm.


  1. RxNorm [1]
  2. Cimino JJ. cimino-desiderata-for-controlled-medical-vocabularies.pdf. [serial on the Internet]. 1989 [cited 2011 May 8]. Available from: http://www.sahs.uth.tmc.edu/evbernstam/hi5300/articles%20(reading%20materials)/cimino_desiderata-for-controlled-medical.pdf Cimino JJ. cimino-desiderata-for-controlled-medical-vocabularies.pdf. 1989.