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RxNav - A Semantic Navigation Tool for Clinical Drugs

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 RxNavRxNorm is one of a suite of designated standards for use in U.S. Federal Government systems for the electronic exchange of clinical health information. RxNorm provides standard names for clinical drugs (active ingredient + strength + dose form) and for dose forms as administered to a patient. It provides links from clinical drugs, both branded and generic, to their active ingredients, drug components (active ingredient + strength), and related brand names. NDCs (National Drug Codes) for specific drug products (where there are often many NDC codes for a single product) are linked to that product in RxNorm. RxNorm links its names to many of the drug vocabularies commonly used in pharmacy management and drug interaction software, including those of First Databank, Micromedex, MediSpan, Gold Standard Alchemy, and Multum. By providing links between these vocabularies, RxNorm can mediate messages between systems not using the same software and vocabulary.

RxNorm, a standardized nomenclature for clinical drugs, is produced by the National Library of Medicine (NLM). In this context, a clinical drug is a pharmaceutical product given to (or taken by) a patient with a therapeutic or diagnostic intent. In RxNorm, the name of a clinical drug combines its ingredients, strengths, and form.

While ingredient and strength have straightforward meanings, clarification of what is meant by form is in order. In RxNorm, the form is the physical form in which the drug is administered or is specified to be administered in a prescription or order. The RxNorm clinical drug name does not refer to the size of the package, the form in which the product was manufactured, its form when it arrived at the dispensary, or the route of administration of the drug..

RxNorm’s standard names for clinical drugs are connected to the varying names of drugs present in many different controlled vocabularies within the Unified Medical Language System (UMLS) Metathesaurus, including those in commercially available drug information sources. These connections are intended to facilitate interoperability among the computerized systems that record or process data dealing with clinical drugs.


A Simple Idea Implemented Rigorously

RxNorm is organized around concepts with normalized names for clinical drugs. These names contain information on ingredients, strengths, and dose forms. For example:

Acetaminophen 500 MG Oral Tablet                      for a generic drug name
Acetaminophen 500 MG Oral Tablet [Tylenol]         for a branded drug name

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. Thus, Acetaminophen 500 MG Oral Tablet is related to Acetaminophen 500 MG Oral Tablet [Tylenol], and both have relationships to Acetaminophen, Acetaminophen 500 MG, and Oral Tablet. Within the UMLS Metathesaurus, Acetaminophen 500 MG Oral Tablet and Acetaminophen 500 MG Oral Tablet [Tylenol] will each be linked to different names that are used for these entities in other vocabularies.


Because every drug information system that is commercially available today follows somewhat different naming conventions, a standardized nomenclature is needed for the smooth exchange of information, not only between organizations, but even within the same organization. For example, a hospital may use one system for ordering and another for inventory management. Still another system might be used to record dose adjustments or to check drug interactions. Several cooperating hospitals might have different systems, and find their data incomparable.

A standardized nomenclature that relates itself to terms from other sources can serve as a means for determining when names from different source vocabularies are synonymous (at an appropriate level of abstraction). The goal of RxNorm is to allow various systems using different drug nomenclatures to share data efficiently at the appropriate level of abstraction.

The Scope of RxNorm

RxNorm contains the names of prescription and many nonprescription formulations that exist in the United States.  However, some items may not be used in the United States.

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. Medications, whether prescription or OTC, with more than three ingredients are not fully represented at the present time.

Additions to the vocabulary will be made as new products are put on the market (see Updates, below). Radiopharmaceuticals, because of the decay in strength over time and the requirement that they be ordered and prepared especially for a given time of administration, are listed only as ingredients.


The Elements of RxNorm

An RxNorm clinical drug name reflects the active ingredients, strengths, and dose form comprising that drug. When any of these elements vary, a new RxNorm drug name is created as a separate concept (explained below). Thus, an RxNorm name should exist for every strength and dose of every available combination of clinically significant ingredients.

Nonnumerical, named elements of the RxNorm clinical drug name are also individual RxNorm terms related by formal criteria to the clinical drug name.

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Last Updated ( Sunday, 13 July 2008 18:27 )  

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