• 09/28/2022

In our last two posts on the topic of ‘Data Standards in Health Informatics’ we provided an overview of data standards in health informatics, and we covered SNOMED CT and ICD data standard in detail.

Before you read this article further, we highly recommend you read Part I and II of the series:

In this penultimate post (of data standards series) we will provide an in-depth view on ‘National Drug Codes (NDC)’ and ‘RxNorm’ data standards . Though both are used – in a loose sense – to provide data standards for drugs, however there are some subtle (and not so subtle) differences that one should be mindful of.

At a high level, NDC is FDA's identifier for drugs and primarily used for drug reimbursement; whereas RxNorm is maintained by National Library of Medicine and primarily used in personal health records applications.

Let’s dive into details…


Hospitals, pharmacies, and other organizations use computer systems to record and process drug information. Because these systems use many different sets of drug names, it can be difficult for one system to communicate with another. To address this challenge, RxNorm provides normalized names and unique identifiers for medicines and drugs. The goal of RxNorm is to allow computer systems to communicate drug-related information efficiently and unambiguously through a semantic interoperation between drug terminologies.

RxNorm’s normalized names for clinical drugs and links to many of the drug vocabularies are commonly used in pharmacy management and drug interaction software, including those of First Databank, Micromedex, and Gold Standard Drug Database.

RxNorm includes the United States Pharmacopeia (USP) Compendial Nomenclature from the United States Pharmacopeial Convention. USP is a cumulative data set of all Active Pharmaceutical Ingredients (API). RxNorm contains the names of prescription and many over-the-counter drugs available in the United States.

It’s important to note that non-therapeutic radiopharmaceuticals, bulk powders, contrast media, food, dietary supplements, and medical devices are all out-of-scope for RxNorm. Medical devices include but are not limited to bandages and crutches.

RxNorm provides a unique RXCUI number (of up to eight digits) for each medication. RXCUI can be used to retrieve a great deal of information. Some FHIR Resources reference RxNorm codes. The NLM provides RxNav, a free RxNorm browser. It also provides a free API, for accessing the codes.

Example: if we search for drug trastuzumab on RxNav, we can see all related Brand Names.

National Drug Codes (NDC)

National Drug Codes (NDC) The National Drug Code (NDC) is a US-specific standard for medications maintained by the US Food and Drug Administration (FDA). It consists of a simple 10 digit, 3-segment number. The first segment indicates the manufacturer/labeler/vendor. The second indicates the product name. The third part indicates the packaging. The same medication can have many NDC codes particularly if its patent has expired so it can be produced as a generic drug by many manufacturers.

In the example below ‘50242’ is identifier for Genentech, ‘132’ corresponds to Herceptin and the last two digits correspond to packaging.

It’s noteworthy that you will not find trastuzumab (which is the normalized drug name for the brand Herceptin) in the NDC directory, however, it’s present RxNorm.


[1] This article has been inspired by Mark L. Braunstein's book: "Health Informatics on FHIR: How HL7's API is Transforming Healthcare (Second Edition)"

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