Drug extension content is not typically authored manually on a concept-by-concept basis. Instead, it is derived from existing national drug dictionaries using a structured and scalable process.
This approach is comparable to the development of terminologies such as LOINC, where content is generated based on combinations of well-defined attributes.
The process begins with mapping the atomic elements of the local drug dictionary to SNOMED CT and related standards. These include:
substances (active ingredients)
dose forms
units of measure
strength representations
SNOMED CT aligns with EDQM (European Directorate for the Quality of Medicines) standards for dose forms. Where local dictionaries also use EDQM, this significantly facilitates mapping and interoperability.
Once atomic elements are mapped, higher-level drug concepts are generated based on combinations identified in the local dictionary.
These include:
Medicinal Products (MP)
Medicinal Product Forms (MPF)
During concept generation:
Existing concepts in the International Edition (MP, MPF, CD) should be reused wherever available
Missing concepts are created in the national extension
These missing concepts may later be submitted for promotion to the International Edition
The generation process is typically implemented as:
an automated bulk creation process
followed by manual review and quality assurance
This hybrid approach balances scalability with clinical and terminological accuracy.
Drug extension development involves several common challenges, including:
Variations in ingredient representation across local dictionaries
Limited granularity in source data (e.g. missing strength or form details)
Rounding rules for strength normalization
Non-normalized strength expressions, including numerator/denominator inconsistencies
Addressing these challenges requires careful normalization and alignment with the SNOMED CT concept model.
Real Clinical Drugs (RCD)
Packaged Clinical Drugs (PCD)
Real Packaged Clinical Drugs (RPCD)
Concepts are typically created algorithmically, using rules derived from the SNOMED CT concept model.
Differences in units of measure and representation conventions