Overview

The SNOMED CT International Drug Model provides a standardized framework for representing medicinal products in a manner that is consistent across countries and healthcare systems. The model is part of the Pharmaceutical / Biologic Product hierarchy and defines a set of concept classes that represent medicinal products at different levels of abstraction.

The international model focuses on representing the clinical characteristics of medicinal products, including:

• active ingredient(s)

• dose form

• strength

These characteristics allow medicines to be represented in a way that is independent of local brand names, packaging, or regulatory authorizations.

The international drug model defines several concept classes that represent medicinal products at different levels of abstraction. These concept classes allow systems to represent medications with the level of detail required for different clinical and administrative workflows.

A Medicinal Product represents a medicinal product defined only by its active ingredient(s). It does not specify dose form or strength.

This level is commonly used for:

• ingredient-based decision support rules

• drug interaction checking

• pharmacovigilance analysis

• high-level reporting and analytics

A Medicinal Product Form represents a medicinal product defined by active ingredient(s) and dose form, but without specifying strength.

This level allows grouping of products that share the same ingredient and pharmaceutical form.

Typical uses include:

• prescribing templates

• clinical decision support rules specific to dose form

• reporting and aggregation

A Clinical Drug represents a medicinal product defined by:

• active ingredient(s)

• strength

• manufactured dose form

This level provides the detail required for most clinical workflows such as prescribing and medication administration.

Clinical Drug concepts represent generic clinical specifications of medicines, independent of brand names or manufacturers.

The concept classes of the international drug model form a hierarchy that supports aggregation and semantic reasoning.

For example:

This hierarchical structure allows:

• aggregation of detailed data for reporting

• decision support rules defined at the ingredient level to apply to all related products

• consistent interpretation of medication data across systems

The international drug model uses a set of defining attributes to describe medicinal products. These attributes allow drug concepts to be formally defined and classified within the SNOMED CT hierarchy.

Common attributes include:

These attributes enable consistent modeling and automated classification of medicinal product concepts.

The international drug model provides the clinical foundation for representing medicinal products, but it does not represent jurisdiction-specific details such as:

• brand names

• authorized products

• packaging information

• pack sizes

These concepts are represented in National SNOMED CT Drug Extensions, which extend the international model to support local regulatory and clinical requirements.

For example:

The international model therefore provides the semantic backbone for national drug extensions, ensuring that medicines can be represented consistently across jurisdictions.

Overview

The SNOMED CT Drug Extension Model provides a standardized framework for representing real-world medicinal products that are authorized and available within a specific jurisdiction.

While the SNOMED CT International Drug Model represents medicinal products in a jurisdiction-independent and abstract manner, national healthcare systems require additional information to support operational and regulatory use cases. These include:

• brand or proprietary names

• manufacturer or marketing authorization holder

• packaging and presentation

• locally authorized and marketed products

Drug extensions address these requirements by extending the international medicinal product hierarchy with additional concept classes that represent specific products and packages, while maintaining semantic alignment with the International Edition.

The extension model ensures that real-world medicinal products can be represented in a way that supports clinical use, supply chain processes, and regulatory requirements, without compromising interoperability.

The drug extension model defines additional concept classes that represent authorized products and their packaging. These concept classes complement the international model and provide the level of detail required for operational workflows.

A Real Clinical Drug (RCD) represents a medicinal product that is authorized and marketed within a specific jurisdiction.

An RCD is defined as a specialization of a Clinical Drug (CD) and therefore includes:

• active ingredient(s)

• strength

• manufactured dose form

In addition, it includes product-specific characteristics such as:

• brand or proprietary name

• manufacturer or supplier

• regulatory authorization

This level is commonly used for:

• pharmacy dispensing

• medication administration

• pharmacovigilance reporting

• reimbursement and billing

Example:

• Clinical Drug (CD):

  Product containing precisely amoxicillin 500 milligram oral capsule (clinical drug)

• Real Clinical Drug (RCD):

  BrandX amoxicillin 500 milligram oral capsule (real clinical drug)

A Clinical Drug Package (CDP) represents a generic packaged medicinal product, defined by packaging characteristics but not tied to a specific branded product.

A CDP is derived from a Clinical Drug and includes:

• pack size

• unit of presentation

• container type

This level is commonly used for:

• procurement specifications

• logistics planning

• supply chain management

Example:

• Clinical Drug (CD):

  Product containing precisely amoxicillin 500 milligram oral capsule (clinical drug)

• Clinical Drug Package (CDP):

  Product containing precisely amoxicillin 500 milligram oral capsule box of 24 (clinical drug package)

A Real Clinical Drug Package (RPCD) represents a specific packaged medicinal product available in the supply chain.

An RPCD combines:

• a Real Clinical Drug (RCD)

• packaging characteristics

This level is commonly used for:

• pharmacy inventory systems

• medication dispensing systems

• supply chain management

• regulatory tracking and traceability

Example:

• Real Clinical Drug (RCD):

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

• Real Clinical Drug Package (RPCD):

  Brand X amoxicillin 500 milligram oral capsule box of 24 (real clinical drug package)

The drug extension model extends the international hierarchy by adding concept classes that represent real-world products and packaging.

The combined model can be illustrated as follows:

This structure reflects two complementary pathways:

• a real product pathway (CD → RCD → RPCD)

• a generic packaging pathway (CD → CDP)

The Clinical Drug Package (CDP) concept class is not shown in this hierarchical representation because it does not form part of the main vertical specialization pathway from abstract to concrete medicinal products.

The diagram illustrates a single lineage of increasing specificity, where each concept is a direct specialization of the previous one:

• MP → MPF → CD → RCD → RPCD

In this pathway, each step adds additional defining attributes to represent the same medicinal product with increasing specificity, culminating in a specific packaged product (RPCD).

In contrast, CDP represents a parallel packaging abstraction:

• A CDP is derived from a Clinical Drug (CD)

• It introduces packaging attributes (e.g. pack size, container type)

• However, it does not represent a specific real-world product, as it lacks product identity (e.g. brand, manufacturer)

Therefore:

• CDP is not a parent of RCD or RPCD

• CDP does not sit on the direct specialization path from CD to RPCD

• CDP exists as a parallel branch used for generic packaging representations

Conceptually, the structure can be understood as:

This distinction is important because:

• The RCD → RPCD pathway supports clinical and operational workflows involving real products

• The CDP pathway supports administrative and logistical use cases such as procurement and planning

This layered structure ensures that:

• clinical meaning is defined internationally, while product-specific details are added nationally

• clinical rules and decision support defined at the international level apply to extension concepts

• aggregation across concept levels remains consistent (e.g. RCD → CD → MP)

• interoperability is preserved across jurisdictions

Drug extension concepts use additional attributes to represent characteristics specific to real-world medicinal products. These attributes are applied in a structured way according to the concept class.

Some attributes are used across multiple extension concept classes (particularly RCD and RPCD) to represent product identity and regulatory context.

These include:

• Has product name (attribute)

• Has manufacturer (attribute)

• Has marketing authorization (attribute)

• Has intended site / jurisdiction (attribute)

These attributes ensure that extension concepts represent real-world authorized products, while remaining linked to their clinical definitions.

All extension concepts ultimately derive from international drug concepts and therefore inherit core defining attributes such as:

• Has active ingredient (attribute)

• Has manufactured dose form (attribute)

• Has presentation strength (attribute)

• Has concentration strength (attribute) (where applicable)

These attributes define the clinical meaning of the medicinal product and remain consistent across international and national content.

RCD concepts extend Clinical Drugs by adding attributes that identify a specific authorized product:

• Has product name (attribute)

• Has manufacturer (attribute)

• Has marketing authorization (attribute)

These attributes distinguish products that share the same clinical definition but differ in branding or regulatory status.

CDP concepts add packaging information to a Clinical Drug:

• Has pack size (attribute)

• Has unit of presentation (attribute)

• Has container type (attribute)

These attributes describe packaging independently of any specific product.

RPCD concepts combine both product identity and packaging:

• product-level attributes (inherited from RCD)

• packaging attributes (as in CDP), including:

  • Has pack size (attribute)

  • Has unit of presentation (attribute)

This allows full representation of the exact packaged product

The Two-Layer Model

The SNOMED CT Drug Model provides a comprehensive framework for representing medicinal products across healthcare systems. It is composed of two complementary components:

• the SNOMED CT International Drug Model, which defines medicinal products in a jurisdiction-independent and clinically focused manner

• the SNOMED CT Drug Extension Model, which represents real-world medicinal products authorized and available within specific jurisdictions

Together, these components support consistent representation of medicines across clinical, operational, and regulatory workflows, while enabling interoperability across systems and countries.

International Drug Model (Clinical Foundation)

The international model provides the clinical definition of medicinal products, focusing on characteristics such as:

• active ingredient(s)

• dose form

• strength

It defines a set of concept classes that represent medicines at increasing levels of detail:

• Medicinal Product (MP) – ingredient only

• Medicinal Product Form (MPF) – ingredient + dose form

• Clinical Drug (CD) – ingredient + dose form + strength

These concepts are:

• independent of brand and packaging

• consistent across jurisdictions

• used for clinical decision support, prescribing, and analytics

Examples:

• Product containing amoxicillin (MP)

• Product containing amoxicillin in oral capsule dose form (MPF)

• Product containing precisely amoxicillin 500 mg oral capsule (CD)

The drug extension model builds on the international model to represent actual medicinal products available in a country, including product identity and packaging.

It introduces additional concept classes:

• Real Clinical Drug (RCD) – a specific authorized product

• Clinical Drug Package (CDP) – a generic packaged form

• Real Clinical Drug Package (RPCD) – a specific packaged product

These concepts are required for workflows that involve real products rather than abstract clinical definitions, such as:

• dispensing and administration

• inventory and supply chain management

• reimbursement and regulatory processes

Examples:

• Brand X amoxicillin 500 mg oral capsule (RCD)

• Amoxicillin 500 mg oral capsule box of 24 (CDP)

• Brand X amoxicillin 500 mg oral capsule box of 24 (RPCD)

The international and extension models form a single, integrated structure, where extension concepts build directly on international concepts.

This structure reflects two complementary perspectives:

• a clinical perspective, which defines what the medicine is

• a real-world perspective, which defines how the medicine is supplied and identified

The SNOMED CT Drug Model can be understood as a progression from abstract to concrete representations:

• MP – What substance is involved?

• MPF – In what form is it administered?

• CD – What is the precise clinical definition (including strength)?

• RCD – Which specific product is used?

In parallel:

• CDP represents packaging at a generic level, without reference to a specific product

This layered approach allows systems to select the appropriate level of detail depending on the use case.

The model is based on a structured set of characteristics that define medicinal products. At a high level:

• the international model defines clinical characteristics

• the extension model adds product identity and packaging characteristics

This separation ensures that:

• clinical meaning remains consistent across all products

• real-world products can be represented without redefining clinical concepts

• systems can move between levels (e.g. from product to ingredient) for aggregation and analysis

By combining a shared international foundation with flexible national extensions, the SNOMED CT Drug Model enables:

• consistent representation of medicines across systems

• safe and precise clinical workflows

• accurate identification of real-world products

• interoperability across jurisdictions

It allows healthcare systems to represent both:

• what a medicine is (clinical definition)

• what product is used in practice (real-world product and packaging)

For clarity, the SNOMED CT drug model distinguishes several levels of abstraction. Each level supports different clinical or administrative workflows.