Integration with Local Drug Dictionaries
Overview
Most countries maintain a national drug dictionary or medicinal product registry, which serves as the authoritative source for:
authorized medicinal products
brand names and manufacturers
packaging and presentation
regulatory and reimbursement information
These national dictionaries are typically used operationally in:
prescribing systems
pharmacy and dispensing systems
reimbursement and regulatory workflows
To enable interoperability and alignment with SNOMED CT, it is necessary to establish systematic mappings between the national drug dictionary and SNOMED CT drug concepts.
In addition, the SNOMED CT drug model is aligned with the ISO IDMP family of standards. As a result, national drug dictionaries that are structured according to IDMP, or that adopt compatible standards, can be mapped more efficiently and consistently to SNOMED CT. This is particularly relevant for key elements such as substances, strengths, and dose forms. For example, the use of dose forms aligned with European Directorate for the Quality of Medicines & HealthCare standard terms facilitates direct or near-direct mapping to SNOMED CT concepts, reducing ambiguity and improving interoperability across systems.
Alignment with National Drug Data Processes
In most jurisdictions, national drug dictionaries are:
maintained by regulatory or national bodies
updated regularly based on product authorizations and withdrawals
structured according to national pharmaceutical standards
The integration with SNOMED CT is therefore not a one-time activity, but part of an ongoing synchronization process between:
the national drug dictionary
the SNOMED CT International Edition
the SNOMED CT national extension (if implemented)
This process is typically managed by the National Release Center (NRC) or an equivalent authority.
Mapping Approach
Mapping from a national drug dictionary to SNOMED CT is typically performed as a semi-automated, systematic process, rather than manual concept-by-concept mapping.
The process generally includes:
mapping atomic elements
such as substances, dose forms, and units of measure
deriving structured drug concepts
based on combinations of these elements (e.g. ingredient + strength + dose form)
linking national product entries to SNOMED CT concepts
at the appropriate level:
Clinical Drug (CD) for clinical definitions
Real Clinical Drug (RCD) for specific products
Real Clinical Drug Package (RPCD) for packaged products
This approach ensures consistency and scalability across large national datasets.
Representation of Mappings
Mappings between national drug dictionaries and SNOMED CT may be represented in different ways depending on national infrastructure.
Proprietary Mapping Representation
In many countries, mappings are maintained within national systems or databases, for example:
as part of the national drug dictionary
within regulatory or reimbursement systems
in dedicated mapping tables
This approach allows tight integration with national workflows but may be less portable across systems.
SNOMED CT Reference Set Representation
Alternatively, mappings may be represented using SNOMED CT reference sets (refsets).
This approach enables:
alignment with SNOMED CT distribution formats (RF2)
versioning and traceability of mappings
reuse across multiple systems within a country
easier sharing between jurisdictions
For national implementations that publish SNOMED CT extensions, representing mappings as refsets is often the preferred approach.
Level of Mapping
National drug dictionaries often contain detailed product information, including:
brand names
manufacturers
packaging
Mappings should therefore be established at the appropriate level of the SNOMED CT Drug Model, typically:
CD (Clinical Drug) for clinical equivalence
RCD (Real Clinical Drug) for specific authorized products
RPCD (Real Clinical Drug Package) for packaged products
In some cases, mappings may also be required at more abstract levels (e.g. MP) for aggregation or reporting.
Maintenance and Synchronization
Mapping between national drug dictionaries and SNOMED CT must be maintained as part of routine national processes.
This includes:
updating mappings when new products are introduced
removing or updating mappings when products are withdrawn
aligning mappings with updates to SNOMED CT releases
ensuring consistency between national data and SNOMED CT content
Because both national drug dictionaries and SNOMED CT evolve over time, synchronization is an ongoing process rather than a one-time activity.