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NLM Announces Enhancement of Drug Naming Standard for Electronic Health Records

The RxNorm standard clinical drug vocabulary produced by the National Library of Medicine (NLM) now contains more accurate and complete connections between National Drug Codes (NDCs) and standard nonproprietary names of medications recommended for use in electronic health records (EHRs). NLM is the world’s largest medical library and a component of the National Institutes of Health. It also includes, for the first time, the complete set of NDCs from Thomson Reuters’ Red Book, a drug database widely used in the health care industry.

NDCs are product identifiers assigned by manufacturers and packagers of drugs in the United States. They are published on medication labels and packages and are often used in pharmacy inventory control and in dispensing and billing for drugs. If a single manufacturer issues the same medication in packages of different sizes (25 tablets, 50 tablets, etc.), each size has a different NDC. If more than one manufacturer produces the same medication, each assigns different NDCs. In contrast, the RxNorm vocabulary creates standard names and identifiers for the combinations of ingredients, strengths, and dose forms (such as Aspirin 325 MG Oral Tablet) that exist in drugs marketed in the United States. This is the information doctors typically include when they write a prescription because they often can’t know the specific product that will be used to fill it. All medication products that contain the same active ingredients, the same strengths, and the same dose forms have the same RxNorm standard name. This standard name is connected to other information in RxNorm that can be used within EHR systems to improve patient safety.

Accurate and complete connections between NDC product codes and RxNorm standard names and identifiers have many potential uses within an individual patient’s EHR. These include the use of an NDC on a medicine bottle to speed standard data entry or to trigger an alert written in the RxNorm standard that could prevent a medication error. At present, there is no single source that contains the NDCs for all medications currently marketed in the United States. RxNorm has included NDCs provided by the Food and Drug Administration, the Department of Veterans Affairs, and the Multum and Gold Standard drug information sources for a number of years. Starting with the Feb. 7, 2011 release, RxNorm included a revised, filtered version of the NDC data that segregates obsolete NDCs from those currently in the marketplace. It also included First DataBank’s set of NDCs. Since August of 2011, it has included the NDCs from Red Book. Other useful data that Red Book is providing to RxNorm includes better linkages between branded drugs and their NDCs, information about whether or not drugs are still on the market, and Drug Enforcement Agency Class for controlled drugs. This additional information is instrumental in the production of the Current Prescribable Subset of RxNorm.

In a recently published study sponsored by the Centers for Medicare & Medicaid Services and performed by the RAND Corporation and others, RxNorm was found to have entries for essentially all of the drugs in a sample of 19,743 ambulatory e-prescriptions (electronic prescriptions for patients seen in clinics or physician offices). Some e-prescriptions in the study sample failed to match automatically to an NDC in RxNorm, however. A more complete set of NDCs is likely to eliminate this gap.

For more information about RxNorm, visit the NLM News Release and the NLM UMLS website.

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