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Vocab. RXNORM_EXTENSION

Janice Cruz edited this page Sep 2, 2024 · 5 revisions

RxNorm Extension

RxNorm Extension is an OHDSI resource to represent international drugs in a structure adapted from RxNorm. This describes 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 in 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 are the following classes:

Concept Class Composed of Remarks
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.

Combined target structure

To incorporate a new set of drug information, a structure that contains every Concept only once and preserves the RxNorm structure, no matter which vocabulary the additional Concept is coming from should be achieved. This means that for each source drug concept a standard concept that follows RxNorm logic is created and correctly placed inside a hierarchy. In a way, it should create a mixed RxNorm/drug vocabularies union.

In order to achieve this, any two equivalent Concepts have to be matched through its components: Ingredients to Ingredients, Forms to Forms, Supplier to Supplier, etc. Concepts are defined as matching if all components match. For example, a Clinical Drug matches another Clinical Drug if it contains the same Ingredients at the same strength and the same Dose Form.

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.

Implementation

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

Result

Concepts belonging to source drug vocabularies have 'Maps to' relations to standard concepts in RxNorm and RxNorm Extension vocabularies.

Equivalence relationship to valid non-standard concepts (like Brand Names and Dose forms) is indicated by entry in CONCEPT_RELATIONSHIP table with RELATIONSHIP_ID = 'Source - RxNorm eq'. Such relations are built for attributes like Dose Forms and Brand Names.

Relationships between Drug Products or derivatives (Drug Forms and Components) are connected through CONCEPT_RELATIONSHIP_STAGE records with the the following relationship_id values:

Concept Class 1 Concept Class 1 Relationship
Brand Name Branded Drug Brand name of
Brand Name Branded Drug Comp Brand name of
Brand Name Branded Drug Form Brand name of
Brand Name Ingredient Brand name of
Brand Name Quant Branded Drug Brand name of
Brand Name Marketed Product Brand name of
Branded Drug Brand Name RxNorm has ing
Branded Drug Branded Drug Comp Consists of
Branded Drug Branded Drug Form RxNorm is a
Branded Drug Branded Pack Contained in
Branded Drug Clinical Drug Tradename of
Branded Drug Clinical Drug Comp Consists of
Branded Drug Dose Form RxNorm has dose form
Branded Drug Quant Branded Drug Has quantified form
Branded Drug Quant Clinical Drug Tradename of
Branded Drug Marketed Product Has marketed form
Branded Drug Comp Brand Name RxNorm has ing
Branded Drug Comp Branded Drug Constitutes
Branded Drug Comp Clinical Drug Comp Tradename of
Branded Drug Comp Quant Branded Drug Constitutes
Branded Drug Form Brand Name RxNorm has ing
Branded Drug Form Branded Drug RxNorm inverse is a
Branded Drug Form Clinical Drug Form Tradename of
Branded Drug Form Dose Form RxNorm has dose form
Branded Drug Form Quant Branded Drug RxNorm inverse is a
Branded Pack Branded Drug Contains
Branded Pack Clinical Drug Contains
Branded Pack Clinical Pack Tradename of
Branded Pack Dose Form RxNorm has dose form
Branded Pack Quant Branded Drug Contains
Branded Pack Quant Clinical Drug Contains
Branded Pack Marketed Product Has marketed form
Clinical Drug Branded Drug Has tradename
Clinical Drug Branded Pack Contained in
Clinical Drug Clinical Drug Comp Consists of
Clinical Drug Clinical Drug Form RxNorm is a
Clinical Drug Clinical Pack Contained in
Clinical Drug Dose Form RxNorm has dose form
Clinical Drug Quant Branded Drug Has tradename
Clinical Drug Quant Clinical Drug Has quantified form
Clinical Drug Marketed Product Has marketed form
Clinical Drug Marketed Product Contained in
Clinical Drug Comp Branded Drug Constitutes
Clinical Drug Comp Branded Drug Comp Has tradename
Clinical Drug Comp Clinical Drug Constitutes
Clinical Drug Comp Ingredient Has precise ing
Clinical Drug Comp Ingredient RxNorm has ing
Clinical Drug Comp Quant Branded Drug Constitutes
Clinical Drug Comp Quant Clinical Drug Constitutes
Clinical Drug Form Branded Drug Form Has tradename
Clinical Drug Form Clinical Drug RxNorm inverse is a
Clinical Drug Form Dose Form RxNorm has dose form
Clinical Drug Form Ingredient RxNorm has ing
Clinical Drug Form Quant Clinical Drug RxNorm inverse is a
Clinical Pack Branded Pack Has tradename
Clinical Pack Clinical Drug Contains
Clinical Pack Dose Form RxNorm has dose form
Clinical Pack Quant Clinical Drug Contains
Clinical Pack Marketed Product Has quantified form
Dose Form Branded Drug RxNorm dose form of
Dose Form Branded Drug Form RxNorm dose form of
Dose Form Branded Pack RxNorm dose form of
Dose Form Clinical Drug RxNorm dose form of
Dose Form Clinical Drug Form RxNorm dose form of
Dose Form Clinical Pack RxNorm dose form of
Dose Form Quant Branded Drug RxNorm dose form of
Dose Form Quant Clinical Drug RxNorm dose form of
Dose Form Marketed Product RxNorm dose form of
Ingredient Brand Name Has brand name
Ingredient Clinical Drug Comp RxNorm ing of
Ingredient Clinical Drug Form RxNorm ing of
Marketed Product Brand Name Has brand name
Marketed Product Branded Drug Marketed form of
Marketed Product Branded Pack Marketed form of
Marketed Product Clinical Drug Marketed form of
Marketed Product Clinical Drug Contains
Marketed Product Clinical Pack Marketed form of
Marketed Product Dose Form RxNorm has dose form
Marketed Product Quant Branded Drug Marketed form of
Marketed Product Quant Clinical Drug Contains
Marketed Product Quant Clinical Drug Marketed form of
Marketed Product Supplier Has supplier
Quant Branded Drug Brand Name RxNorm has ing
Quant Branded Drug Branded Drug Quantified form of
Quant Branded Drug Branded Drug Comp Consists of
Quant Branded Drug Branded Drug Form RxNorm is a
Quant Branded Drug Branded Pack Contained in
Quant Branded Drug Clinical Drug Tradename of
Quant Branded Drug Clinical Drug Comp Consists of
Quant Branded Drug Dose Form RxNorm has dose form
Quant Branded Drug Quant Clinical Drug Tradename of
Quant Branded Drug Marketed Product Has marketed form
Quant Clinical Drug Branded Drug Has tradename
Quant Clinical Drug Branded Pack Contained in
Quant Clinical Drug Clinical Drug Quantified form of
Quant Clinical Drug Clinical Drug Comp Consists of
Quant Clinical Drug Clinical Drug Form RxNorm is a
Quant Clinical Drug Clinical Pack Contained in
Quant Clinical Drug Dose Form RxNorm has dose form
Quant Clinical Drug Quant Branded Drug Has tradename
Quant Clinical Drug Marketed Product Has marketed form
Quant Clinical Drug Marketed Product Contained in
Supplier Marketed Product Supplier of

Name of the Branded and Clinical Pack concepts is built by combining names of the contents.

Relationships between any Drug Concept Class and a Classfication Concept Class is recorded through the “Drug has drug class” and “Drug class of drug” generic relationship pair.

Inferring of missing Concept Classes

After RxNorm Extension Standard concept with the fullest attribute set is created for each source entity, all missing preceding Concept Classes are inferred from the existing ones, from bottom upwards.

Concept Class Defined by
Clinical Drug Component Ingredient-strength. Note that Clinical Components are always single-Ingredient. This is in contrast to all other Concept Classes
Branded Drug Component Ingredient-strength(s), Brand Name
Clinical Drug Form Ingredient(s), Dose Form
Branded Drug Form Ingredient(s), Dose Form, Brand Name
Clinical Drug Ingredient-strength(s), Dose Form
Branded Drug Ingredient-strength(s), Dose Form, Brand Name
Quantified Clinical Drug Ingredient-strength(s), Dose Form, Quantity
Quantified Branded Drug Ingredient-strength(s), Dose Form, Brand Name, Quantity
Clinical Drug Box Ingredient-strength(s), Dose Form, Box size
Branded Drug Box Ingredient-strength(s), Dose Form, Brand Name, Box size
Quantified Clinical Box Ingredient-strength(s), Dose Form, Quantity, Box size
Quantified Branded Box Ingredient-strength(s), Dose Form, Brand Name, Quantity, Box size

Even though all drug classes are inferred, only those will be created as concepts that have no mapping to an existing equivalent Standard Concept.

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