RXNORM to SNOMED mapping

Question

We have medications listed in our medical system. They are mapped to RxNorm ids.

We want to migrate to Snomed. Is there a way to match RxNorm ids to Snomed concept ids? Perhaps there is a database with links? Or a service?

Answer 1

SNOMED and RXNORM are very different in how they represent drug information. RXNORM is much more complete and encodes strength, administration route, packaging information and product names. SNOMED has mainly principal active ingredients and some product names. The coverage in SNOMED for strength and administration route is not great.

For instance SNOMED does not have IDs for Prozac but does have for Fluoxetine which is the principal ingredient of Prozac

In RXNORM you can find the following connections:

[PROzac Weekly 90 MG Delayed Release Oral Capsule]
-- ingredient --> [Prozac] 
-- precise ingredient --> [Fluoxetine]

And the ingredient concept will take you to SNOMED:

[Fluoxetine] --> SNOMEDCT_US:53640004 SNOMEDCT_US:372767007

Bear in mind that most ingredient in SNOMED are duplicated as product and substance and each of these types give different relations.

Three options to implement this:

1. Use the RXNORM/NIH NLM data files https://www.nlm.nih.gov/research/umls/rxnorm/docs/rxnormfiles.html
2. BioPortal API (free) http://bioportal.bioontology.org/
3. Lexigram API (commercial) http://www.lexigram.io/

The important aspect here is that if you replace RXNORM IDs with SNOMED IDs you will be losing information but of course depending on your use case that might be just fine. I would consider using NDCs.

Disclaimer: I was an engineer at BioPortal and currently CTO at Lexigram.