Content Representation

SNOMED CT Extension Format – Drug Content in RF2

Overview

SNOMED CT drug content, whether part of the International Edition or a national drug extension, is distributed using Release Format 2 (RF2). RF2 provides a structured, tabular representation of terminology components, enabling consistent storage, exchange, and processing of SNOMED CT data.

In RF2, a medicinal product is not represented as a single record, but as a set of coordinated entries across multiple files:

• the Concept file identifies the drug concept

• the Description file provides human-readable names

• the Relationship file defines the meaning of the drug

• Reference sets (refsets) provide additional context such as language preferences and mappings

Each row in these files represents a single component, and together they form a computable definition of a medicinal product.

Example Scenario: Representing a Real Drug

Consider the following real-world product:

Brand X amoxicillin 500 mg oral capsule (real clinical drug)

In RF2, this product is reconstructed from multiple components across files.

Concept File – Identifying the Drug

The Concept file contains one row per concept. For a drug, this row represents the existence of the medicinal product.

id        effectiveTime  active  moduleId     definitionStatusId
999001234 20250131       1       EXT_MODULE   Fully defined

In drug context:

• This row represents the Real Clinical Drug (RCD) concept

• The concept itself has no meaning without descriptions and relationships

• It acts as the anchor identifier for all related information

👉 Think of this as: “This drug exists in the terminology.”

Description File – Naming the Drug

The Description file provides the human-readable terms associated with the concept.

id      conceptId   typeId   term
888001  999001234   FSN      Brand X amoxicillin 500 mg oral capsule (real clinical drug)
888002  999001234   Synonym  Brand X amoxicillin 500 mg capsule

In drug context:

• The Fully Specified Name (FSN) provides a precise and unambiguous description of the medicinal product

• Synonyms provide alternative terms used in prescribing, dispensing, and user interfaces

The acceptability of synonyms (e.g. which term is preferred for display) is not defined in the Description file itself. Instead, it is specified in a Language Reference Set, which indicates:

• which synonym is the preferred term

• which synonyms are acceptable alternatives

👉 This allows different countries or systems to use different preferred terms for the same drug concept, while maintaining a shared underlying identifier and meaning.

Relationship File – Defining the Drug

The Relationship file represent the defining properties (the definition) of the drug using structured relationships.

Each row represents a single relationship between concepts.

Clinical Definition (Inherited from International Model)

sourceId   typeId                      destinationId
999001234  Has active ingredient      Amoxicillin
999001234  Has dose form              Oral capsule
999001234  Has strength               500 mg

In drug context:

These relationships define the clinical meaning of the drug:

• what substance it contains

• how it is administered

• how strong it is

👉 This corresponds to the Clinical Drug (CD) definition.

Product Identity (Extension-Specific)

sourceId   typeId                 destinationId
999001234  Has product name      Brand X
999001234  Has manufacturer      Company Y

In drug context:

These relationships distinguish this concept as a Real Clinical Drug (RCD):

• same clinical definition as other amoxicillin 500 mg capsules

• but a specific branded and authorized product

👉 This is what makes it usable in dispensing and traceability.

Packaging Example – Moving to RPCD

Now consider:

BrandX amoxicillin 500 mg oral capsule box of 24 (real clinical drug package)

This concept includes additional packaging relationships:

sourceId   typeId                  destinationId
999009999  Has pack size           24
999009999  Has unit of presentation Capsule
999009999  Is a                    Real clinical drug package

In drug context:

• These relationships describe how the product is packaged and supplied

• Combined with product identity, this forms a Real Clinical Drug Package (RPCD)

👉 This level is used in inventory, logistics, and dispensing systems.

Mapping to Local Drug Dictionaries

In addition to SNOMED CT content, extensions often include mapping artifacts that link SNOMED CT concepts to local drug dictionary identifiers.

These mappings support:

• interoperability between systems

• migration from legacy terminologies

• integration with national regulatory and reimbursement systems

Reference Sets – Adding Context

Reference sets provide additional, non-defining information.

Example: Mapping to a National Drug Code

referencedComponentId   mapTarget
999001234               AMOX500_BRANDX

In drug context:

• Links the SNOMED CT concept to a local drug dictionary or regulatory identifier

• Supports integration with pharmacy, billing, and regulatory systems

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