We would like to convert from RxNorm medications to their ingredients. RxNorm is an ontology, with terms connected by relationship types, which can be traversed to map ingredients. This is necessary to map RxNorm medications to DrugBank, enabling network inclusion. Additionally, we need to know when medications map to multiple ingredients as we are excluding combination therapies for the time being. Once the mapping is complete, we can proceed with integrating the ehrlink resource. This discussion will follow our attempts to map concepts to ingredients.
RxNorm term types
RxNorm concepts each have a specified term type (TTY). RxNorm documentation is oftentimes difficult to navigate, so we provide definitions for all term types below. The descriptions are from , while definitions were found here.
dose form group
The term type (TTY) indicating that this name is that of the substance represented in an RxNorm name responsible for the medicinal activity. Also, the name and the substance.
The TTY indicating that this name is that of the ingredients of a combination product represented in an RxNorm name, where those ingredients are responsible for the medicinal activity. Also, the name and the substances.
The TTY indicating that this name is that of the substance, expressed more precisely as a salt or ester of the ingredient, represented in an RxNorm name. Also, the name and the substance expressed precisely.
The TTY indicating that this name is the normalized name created for a branded clinical drug. The name consists of ingredient, strength, and dose form, followed by a brand name in square brackets. Also, the name and the product.
branded drug component
branded dose form
branded dose form group
clinical drug component
clinical dose form
clinical dose form group
RxNorm API method
We found a method to retrieve ingredients using the allrelatedRxNorm API command. An example query for rxcui 198440 looks like:
To go further on resolving ambiguities when retrieving concepts, I had to look up abbreviations of the TTY too. I had seen the very useful link you mention above from the RxNav documentation, but I finally used the more general ressource that is the MetaThesaurus of UMLS. This page lists all the abbreviations used in the Rx system.
I extracted from this page the table with all the TTY abbreviations into a reusable csv file. It could be useful down the road to other people.