Terms Of Service
In order to avoid overloading the RxNav servers, NLM requires that users of the APIs (RxNorm, RxTerms, NDF-RT, 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 contact us. NLM staff will evaluate your request and determine if an exception may be granted.

You may also consider using RxNav-in-a-Box, the locally installable version of our RESTful APIs based on Docker containers.

We invite you to develop computer and mobile applications using National Library of Medicine (NLM) resources. 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.

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.

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.