RxNorm
Normalized Names for Clinical Drugs
What is RxNorm?
A standardized clinical terminology for the United States built to support capture of clinical drug (or medication) information in electronic medical records systems and for e-prescribing. It has terms and codes representing all forms of medications approved for use by the U.S. Federal Drug Administration (FDA). For example,
According to National Library of Medicine (NLM), RxNorm is two things: a normalized naming system for generic and branded drugs; and a tool for supporting semantic interoperation between drug terminologies and pharmacy knowledge base systems.
RxNorm started as an NLM project in 2001 to develop an approach for modeling and standardizing medication names in the Unified Medical Language System (UMLS). The UMLS already contained a number of different drug terminologies that named medications in very different ways, especially regarding features such as dose forms and routes of administration. This led to a significant amount of missed synonymy and an inability to use drug information consistently in electronic systems. Eventually, this grew into a fully-fledged terminology with a consistent model for representing different aspects of clinical drugs in the way that patients use or are administered them.
What content is in RxNorm?
RxNorm currently contains more than 37,000 clinical drug concepts and over 20,000 branded forms of those medications. In total, there are over 200,000 codes used to represent all of the features of the RxNorm model.
Each “clinical drug” concept in RxNorm has a supporting graph that links to “components” (representing ingredients+strengths), active ingredients, the salt-forms of inactive ingredients, brand names, branded forms of the clinical drugs, dose forms (and dose form groups), and packages of drugs (such as birth control pills that may contain more than one specific kind of clinical drug).
RxNorm offers standard naming conventions for each element in a graph as well as linking to corresponding codes from a variety of other UMLS terminologies that contain medications. It incorporates a number of data feeds that allow it to be very dynamic, with weekly “add only” versions, and full monthly releases of the entire terminology.
A common use case when working with medications is to work with “drug classes” - which group medications by one or more aspects or features of the actual substances involved. For example, “mechanism of action” or “pharmacokinetics”. RxNorm does not itself assert drug class information but does contain linkages to a number of other terminologies that do provide a class-level view of the RxNorm content. One publicly available tool for this is RxClass, hosted by the NLM.
How is RxNorm used in the United States?
RxNorm a key standard clinical terminology within the United States. According to the National Library of Medicine (NLM), which distributes SNOMED CT in the U.S., it is one of a suite of designated standards for use in U.S. Federal Government systems for the electronic exchange of clinical health information and is also a required standard in interoperability specifications of the U.S. Healthcare Information Technology Standards Panel.
One can clearly see the importance of RxNorm in U.S. Healthcare by looking at the United States Core Data for Interoperability (USCDI), published by the Office of the National Coordinator (ONC). RxNorm is a widely adopted standard for vaccine products, patient medications, and in coding medications involved in allergies. RxNorm is not used outside the United States as it is tightly bound to the legal prescribibility of medications as authorized by the FDA.
How is RxNorm related to other healthcare standards efforts?
The National Library of Medicine itself has a wide variety of collaborations and an important role in healthcare standards within the United States. RxNorm is just one product of the library and collaborates primarily with other federal government agencies to provide data feeds (such as the “standard product label”). The terminology itself contains clinical drug information from at least 13 other terminologies (with varying license restrictions) including United States Pharmacopeia (USP) Compendial Nomenclature from the United States Pharmacopeial Convention.