Terminology Services
Terminology services provide the core infrastructure for accessing, querying, and validating SNOMED CT drug content. They enable systems to use the SNOMED CT Drug Model in a computable and scalable way, supporting both clinical workflows and analytical use cases.
A terminology service acts as the intermediary between:
the RF2 terminology content (International + Drug Extension)
the applications and APIs that consume drug data
Core Capabilities
A terminology service used for SNOMED CT drug content should support the following capabilities:
Concept lookup
Retrieve details of a concept (e.g. term, status, relationships)
Hierarchy traversal
Navigate parent–child relationships across the drug hierarchy (e.g. MP → CD → RCD)
Subsumption testing
Determine whether one concept is a subtype of another (e.g. whether a product contains a given ingredient)
Value set expansion
Generate a set of concepts based on defined criteria (e.g. all drugs containing a substance)
Expression Constraint Language (ECL) execution
Perform dynamic, logic-based queries over SNOMED CT content
These capabilities are essential to support:
clinical decision support
product selection and substitution
reporting and analytics
interoperability between systems
Role of Terminology Services in the Drug Model
Terminology services are particularly important for the SNOMED CT Drug Model because they enable:
navigation across abstraction levels
(e.g. linking CD → RCD → RPCD)
dynamic grouping of drugs
(e.g. all products containing an ingredient)
clinical reasoning
(e.g. interaction checking, dose validation)
interoperability across systems
(e.g. consistent interpretation of medication data in FHIR workflows)
FHIR Terminology Services
FHIR-based terminology services provide standardized APIs for accessing SNOMED CT content. These APIs enable consistent use of drug terminology across systems.
Key operations include:
$expand
Expands a value set into a list of SNOMED CT concepts
(e.g. all drugs containing a specific ingredient)
$validate-code
Validates whether a code is valid within a given value set or system
(e.g. checking if a selected drug is a valid Clinical Drug)
$subsumes
Determines hierarchical relationships between concepts
(e.g. whether a dispensed product is a subtype of a prescribed drug)
Implementation Considerations
When implementing terminology services for drug content, systems should ensure:
support for ECL queries involving attributes (ingredient, dose form, strength)
efficient handling of large extension datasets
alignment between terminology services and FHIR APIs
consistent use of value sets across workflows
Because drug data is both hierarchical and highly structured, terminology services are not optional—they are a core dependency for safe and effective implementation of the SNOMED CT Drug Model.