Model overview

The diagram below shows the concept classes for the extension model with, and related to, the concept classes in the international release model for medicinal products.  No role or grouper concept classes that are parents of the the Medicinal Product (MP) class in the international release are shown in the diagram; it is expected that all grouping classes - based on substance structure, disposition and therapeutic role - will be inherited from the international release.   For all of the classes of the national extension model for representation of medicinal products the closed world view is applied; products are defined using only the active ingredient substances as authorised by the regulatory agency in the particular jurisdiction of use; packs are defined using only the clinical drug concepts that they are composed of (contain) (see also section 8 below).

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Figure 1: Diagram of the classes of the SNOMED CT national extension model for Medicinal Products

In the diagram, the MP classes are shown in shades of blue, the MPF classes in shades of yellow, the CD classes in shades of green and the PCD classes in shades of orange; the concepts represent the real world medicinal products available within a nation and described within that extension are shown in the darker brighter shades.

Classes of National Extension Model

The five concept classes of the international release are shown on the left hand side in their three levels or groups (MP, MPF and CD), with their two representations - the "containing" and the "only" - of the open and closed world views respectively.  The sixth and optional class of MP Precise Only Precisely is also shown, as l that class that may be used in a national extension model if required.  Definitions, descriptions and examples of the five concepts in these classes can be found in the SNOMED CT Medicinal Product Model Specification.  No requirement has been identified to date to suggest that the MPF class from the international core requires a mirrored class in the national extension model.  

The classes of the national extension model are, with the exception of the PCD, shown on the right hand side: two of the classes of the national extension model 'mirror' classes in the international model; their concepts represent the real world medicinal products available within a nation that are types of the concepts in the international release:

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Then there are two classes in the national extension model represent classes that are more granular specific than the classes of the international model in that they represent real medicinal products as they are presented into the supply chain in packages for clinical/patient use (the aggregate product use  in a particular country.  Any sub-packaging used inside a single package (for example, blister strips) and the aggregate packaging used in wholesaling and delivery such as boxes shrink-wraps and pallets are excluded). These The two additional package classes are

• the Real Packaged Clinical Drug (RPCD) which is a representation of a packaged product marketed by a single organisation (manufacturer or supplier) under a single name (which may be a trade or brand name) which contains one or more Real Clinical Drugs within it, in set amounts
• the optional Packaged Clinical Drug (PCD) which is an abstract representation of the Real Packaged Clinical Drug, in that it has no manufacturer or supplier information and therefore represents a package containing one or more Clinical Drugs within it, in set amounts

All the concept classes in the national extension model use the "closed world view" and therefore include the ingredient count attributes because when describing the real products that are authorised for supply in a country, what is stated about them must be true and only what is stated can be true.  

No requirement has been identified to date to suggest that the MPF class from the international core requires a mirrored class in the national extension model.

Definitions and detailed descriptions of the extension classes are given in the sections below this model introduction.

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Extensions may wish to populate and use all of the classes described in the model, or they may wish to use only a subset; it is envisaged that the Clinical Drug class from the international core will be foundational, associated with the Real Clinical Drug in a national extension, but all others may be considered optional for implementation.

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Similarly, some nations may require the MP Precise Only Precisely concept for some classes of concepts medicines where the precise ingredient substance can affect the clinical characteristics such as potency (e.g. glucocorticosteroids) if these concepts need to be available to support "dose based prescribing" (i.e. prescribing that specifies a medicine concept plus a route of administration, a dose quantity and a dose frequency, but does not specify a dose form or a strength so therefore not a clinical drug with its precise ingredient substance).  MP Precise Only Precisely concepts can be authored in a national extension using the principles given in the international model specification (see section 3.1.3 of the International Specification).

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The model uses the standard generalisation/specialisation relationship between the mirrored "Realreal" classes of the national extension and their abstract classes in the international core, and then .   It also uses a partitive relationship, shown in the diagram as the specialised composition relationship (the 'live together, die together' relationship), between the Clinical Drug and Packaged Clinical Drug classes, indicating that the Packaged Drug classes are "composed of" concepts that are themselves Clinical Drugs. The .  This is reflected in the "contains clinical drug" attribute that is part of the logical definition of a Packaged Clinical Drug.   The composition relationship is particularly appropriate for those packaged medicinal products that contain more than one clinical drug (often referred to as "kit products"). The combination of the usual SNOMED CT generalisation relationship and partitive relationship is manageable within the SNOMED CT tooling and will be applicable for description of other types of product concepts within the overall scope of SNOMED CT such as medical devices, which are often composed of more than one type of entity (e.g. drug eluting stents). The use of the composition relationship between Clinical Drugs and Packaged Clinical Drugs means that if implementations wish to display Packaged Clinical Drugs with a direct relationship to the Clinical Drugs that they contain (as in "under" the Clinical Drugs and them in a hierarchical display) nd they wish to transfer information such as the therapeutic role from the Clinical Drug to the Packaged Clinical drug Drug that they are related to, this composition relationship and the 'contains clinical drug' attribute must to be used to facilitate that.  

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The international core content of SNOMED CT will provide all the attribute relationships (see detail below) needed to define medicinal product concepts in a national extension. These will be suitably defined according to SNOMED machine-readable concept model (MRCM) principles and available for use in the tooling. However, not all the The concepts to provide the values for those attributes can the product name and supplier cannot be present in the core (the product names for the Real Medicinal Product etc. and the supplier organisations) and as such, this specification International edition as these do not have international applicability or even international uniqueness (especially for product name).  This specification therefore cannot provide ranges for those these attributes; however the supertype concepts will be available are available (774167006 | Product name (product name) | and 774164004 | Supplier (supplier) |) to support extension authoring.

For various reasons, not all the individual Medicinal Product and Clinical Drug concepts that a nation requires may be present in the international coreInternational edition; some additional content may require authoring in the nation's own extension. However all All the substance, strength, dose form and pack unit , unit of presentation and package type concepts to value the attributes should be available in the core international content to satisfy the interoperability use cases for the medicinal product hierarchy.  .  Strengths can be described accurately using the appropriate integer or decimal, following editorial rules.

All concepts in the classes of the national extension model should be modelled using the proximal primitive parent modelling pattern and be fully defined wherever possible, using the attribute relationships and values from the international content for the core the substance, strength and dose form and unit of presentation concepts and values from the national extension for product names and manufacturer/supplier organisations, but it is accepted that some primitive concepts may have to be authored.