Terms of Service

DISCLAIMER: It is not the intention of NLM to provide specific medical advice, but rather to provide users with information to better understand their health and their medications. NLM urges you to consult with a qualified physician for advice about medications.

Information Content

RxNav, RxNorm API, Prescribable RxNorm

  • RxNav and the RxNorm API provide non-proprietary content from RxNorm, developed by the National Library of Medicine.

RxClass, RxClass API

  • RxClass and RxClass API provide content from SNOMED CT, developed by SNOMED International.

SNOMED CT® Usage Conditions

RxClass includes SNOMED Clinical Terms® (SNOMED CT®) which is used by permission of the International Health Terminology Standards Development Organisation (IHTSDO). All rights reserved. SNOMED CT® was originally created by the College of American Pathologists. “SNOMED”, “SNOMED CT” and “SNOMED Clinical Terms” are registered trademarks of the IHTSDO.

Use of SNOMED CT in RxClass is subject to the SNOMED CT Affiliate license provisions (incorporated in the License Agreement for Use of the UMLS Metathesaurus as Appendix 2) issued by the National Library of Medicine on behalf of SNOMED International.

RxTerms API

    The RxTerms API provides content from RxTerms, developed by the National Library of Medicine.

Interaction API

    The Interaction API uses two sources for its interaction information - ONCHigh and DrugBank.
  • ONCHigh is a list of high-priority drug-drug interactions derived by a panel of experts and contained in a JAMIA article. ONCHigh is updated using CredibleMeds  with drugs that have a known risk of Torsades de Pointes (TdP).
  • DrugBank contains the drug-drug interactions contained in the DrugBank database  . DrugBank does not contain severity level information for the drug-drug interactions.

DrugBank Disclaimer: DrugBank is intended for educational and scientific research purposes only and you expressly acknowledge and agree that use of DrugBank is at your sole risk. The accuracy of DrugBank information is not guaranteed and reliance on DrugBank shall be at your sole risk. DrugBank is not intended as a substitute for professional medical advice, diagnosis or treatment.

Citing DrugBank: Wishart DS, Knox C, Guo AC, Shrivastava S, Hassanali M, Stothard P, Chang Z, Woolsey J. DrugBank: a comprehensive resource for in silico drug discovery and exploration. Nucleic Acids Res. 2006 Jan 1;34(Database issue):D668-72. 16381955

With one exception, no license is needed to use these APIs.

Your Own Apps

We invite you to develop computer and mobile applications using National Library of Medicine (NLM) resources, including our APIs (RxNorm, RxTerms, Prescribable RxNorm, RxClass and Interaction), online or through the locally-installable version, RxNav-in-a-Box. We request that any application that makes use of NLM data include the following statement:

  • "This product uses publicly available data from the U.S. National Library of Medicine (NLM), National Institutes of Health, Department of Health and Human Services; NLM is not responsible for the product and does not endorse or recommend this or any other product."

Developers may not use the NLM name and/or logo in conjunction with their applications.

Online Service

In order to avoid overloading the RxNav servers, NLM requires that users of the APIs (RxNorm, RxTerms, Prescribable RxNorm, RxClass, and Interaction) send no more than 20 requests per second per IP address. Requests that exceed this limit may not be serviced, and service will not be restored until the request rate falls beneath the limit. To limit the number of requests that you send to the APIs, NLM recommends caching results for a 12-24 hour period. This policy is in place to ensure that the service remains available and accessible to all users.

If you have a specific use case that requires you to send a large number of requests to one of our APIs, and thus exceed the request rate limit outlined in this policy, please consider using RxNav-in-a-Box, the locally installable version of our RESTful APIs based on Docker containers.