Wednesday, November 2, 2011

The Benefits of RxNorm

I was recently asked about the benefits of RxNorm and asked my friends at the National Library of Medicine for the answers:

1.       What are the benefits of RxNorm over NDC, or SNOMED?

RxNorm represents drugs in a way that corresponds directly to a prescriber's view of a drug, as an ingredient + strength + dose form. The dose form is the form as it is actually administered (e.g. 'Injectable suspension"), not necessarily the form as it is manufactured and delivered to a pharmacy (e.g. 'Powder for suspension). The NLM has taken government and commercial sources of data, creating normalized names to produce a complete list of the drugs used in the United States. We have a very slim policy-making process, allowing us to respond quickly and effectively to tweak our model if necessary, which we have done a number of times.

The benefit of this approach is that the drugs are named consistently, the names and codes are centrally published and maintained, improvements can be incorporated quickly, and the set of drugs is complete (for the U.S.).

NDC codes represent drugs from what might be called an 'inventory' perspective. NDCs characterize and differentiate drugs on the basis of manufacturer and package size, for example. Two different NDCs could correspond to a singe RxNorm identifier; a generic drug could be made by different manufacturers or provided in different package sizes. NDCs require the use of a 'representative NDC' in order to provide a single identifier for a single clinical drug. Schemes of representative NDCs has proven to be very clumsy to use here in the US. In addition, NDCs are not centrally assigned or maintained. Each manufacturer/packager issues its own NDCs and there is no 'official list' of all NDCs in the US.

SNOMED CT is an international terminology that has a relatively complex editorial process, and requires license fees and participation in its governing organization, the International Health Terminology Standards Development Organization (IHTSDO). The SNOMED CT International Release is meant to contain the 'common denominator' of drugs across the world; each country using SNOMED CT for drugs needs to develop a National Extension separate from the International Release.

2.       What evidence is there for its use, that it has worked successfully and in which hospitals?

RxNorm has been tested by the US Centers for Medicare and Medicaid (CMS) in both a live and a 'lab' environment and found to be complete and usable. Some minor challenges noted in some details of implementation, but overall it was found extremely useful and work-able.

For a variety of reasons having to do with legacy workflows in the US, RxNorm is not currently used in e-prescribing (sending prescriptions from a prescriber to a pharmacy). However it is used in both research and in after-the-fact analysis of drug data in institutions like Stanford Hospital and  University of Florida.

3.       What is the current percentage of hospitals using RxNorm, and what has been the uptake over the last few years in the US, forecast for the next few years?

The standards environment in the US is quickly converging upon RxNorm as the designated drug vocabulary for sending electronic messages containing drug content, and I anticipate that RxNorm will be mandated for many of these uses within the US very shortly.

Thanks to the NLM for this and I look forward to continued implementation of RxNorm in my own institution.


Steven Waldren said...

Have you looked at NDF-RT? Therapeutic classification of drugs is important in the arenas of clinical decision support, medication reconciliation, and quality measurement.

Need to get the mapping between RxNorm and NDF-RT beefed up (

Thanks for the post.


Unknown said...

This was a good blog, I was wondering if you had any recommendations as to where I could search to find clear definitions of both RxNORM and NDF-RT?