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RxNorm Extension - an OHDSI resource to represent international drugs

The purpose of this document is to define the process, rules and resulting structure of incorporating international drug vocabularies into an overall RxNorm-like system, called RxNorm Extension.

Drug vocabularies contain drug products and their components. Only about a third of these products are identical in the drug markets of individual countries or jurisdictions of a drug marketing approval agency. Even if the active ingredients are the same, they can differ in their Drug Strengths, Drug Forms, Brand Names, package sizes and manufacturers or distributors.

Therefore, these vocabularies need to be incorporated into the existing Drug Domain in such a way that all existing drugs and their components are correctly mapped, and the missing ones added as new concepts. This includes a life cycle for each Concept, allowing to generation, deprecation and update over time.

The processing script that follows these instructions can be found here.

General structure

The Drug Domain should be organized in a hierarchical structure described Drug Domain. This structure is based on RxNorm, which also forms the core of the content. RxNorm comprehensively describes the drug market in the United States. It may not contain products sold in the markets of other countries. It also does not contain US medical food or food supplement products.

This structure contains at a minimum (from bottom to top):

Concept Class Composed of
Branded Drug Ingredients, their strength, form, brand name
Clinical Drug Ingredient, their strength, form
Branded Drug Form Ingredient, form, brand name
Clinical Drug Form Ingredient, form
Branded Drug Component Ingredient, strength, brand name
Clinical Drug Component Ingredient, strength
Dose Form Form
Brand Name Brand name
Ingredient Ingredient
Drug Class Drug class

It may optionally contain

Concept Class Composed of
Marketed Product Ingredients, their strength, form, supplier (brand name and box size are optional)
Quantified Branded Drug Box Ingredients, their strength, form, brand name, size and box size
Quantified Clinical Drug Box Ingredients, their strength, form, size and box size
Branded Drug Box Ingredients, their strength, form, brand name and box size
Clinical Drug Box Ingredients, their strength, form and box size
Quantified Branded Drug Ingredients, their strength, form, brand name, size
Quantified Clinical Drug Ingredients, their strength, form, size
Branded Pack Branded Drugs, their number (box size is optional)
Clinical Pack Clinical Drugs, their number (box size is optional)
Supplier Supplier

Currently not supported in the Standardized Vocabularies:

Concept Class Composed of Note
Precise Ingredient Ingredient Ingredient used instead; Precise Ingredients are mapped to Ingredients inside CONCEPT_RELATIONSHIP table
Multiple Ingredient Ingredients Single ingredients used instead
Dose Form Group Dose Form Explicit Dose Forms used instead; Dose Form Groups exist as Classification concepts and bear relation to standard concepts only inside native RxNorm vocabulary

The Concepts are connected through hierarchical and lateral relationships.

Rules for adding Concepts

To add a Concept for which there is an existing equivalent:

  • It should be recorded as a non-standard (source) Concept.
  • It should be mapped through a “Maps to” relationship to its standard equivalent.
  • All other relationships are optional and for QA and convenience. The standard Concept will take its place as the official representation.

To add a Concept that does not have an equivalent:

  • It should be recorded as a standard Concept (standard_concept = 'S'), with the exception of Brand Names, which should be recorded as a non-standard Concepts.
  • It should have hierarchical and lateral relationships in the same manner as RxNorm Concepts do.
  • It should form relationship to relevant drug classes. The relationship_id of these relationship do not have to follow the RxNorm standard, as it differs for every drug class. Classes are most often defined for Ingredients, but some non-Ingredients may directly designate a Concept Class and “jump over” the Ingredient or even Drug Forms or Drug Components. They will be inferred automatically.

Units used in the strength determination are not added. They must be mapped to a Standard UCUM Concept instead. If a unit is not present in the UCUM vocabulary it has to be added.

Concepts from source vocabularies must be added following International drugs vocabulary implementation process.

documentation/international_drugs.1563802859.txt.gz · Last modified: 2019/07/22 13:40 by ekorchmar