This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Previously, the substances hierarchy in SNOMED CT was organized using a number of different axes, some of which did not comply with the terminological principle of being always true. This resulted in incorrect inferences both within the substance hierarchy and in other hierarchies where substances were used to define concepts. To avoid this, the substances hierarchy has been organized by characteristics that are always true (e.g., chemical structure). For substances where the structure is unknown or the substance is heterogeneous, other characteristics that are always true should be used as parent concepts within the substances hierarchy.

The current substances top level hierarchy includes a number of grouper concepts that are role- or use case-based. The proposal is to create a substances top level hierarchy as below.

The grouper concepts that are retained as top level substance concepts will need review of their descendants, but ultimately, it should provide a consistent hierarchy.

There are similarities in the scope of ISO 11238 Health informatics – Identification of medicinal products – Data Elements and Structures for the Unique Identification and Exchange of Regulated Information on Substances and the SNOMED CT substances revision, since both consider a substance to be defined by properties such as molecular structure, and not by how it is formulated or used.

IDMP groups substances as being one of five types of single substances:

• (simple) chemical

• protein/peptide

• nucleic acid

• polymer

or they are classified as a mixture.

In IDMP, the definition of a mixture is much broader that would be perceived by clinical users. IDMP defines starches as mixtures, and also compounds, such as isophane insulin and gentamicin sulfate, as mixtures. This broad definition for mixtures would mean that many of the SNOMED CT substances would be classified as mixtures. These IDMP types are not represented in SNOMED CT, since they are not mutually exclusive and are open to some interpretation. The IDMP documentation does provide guidance on the selection of the correct type for a substance but also acknowledges that a single substance may have two separate type definitions. In addition, the use of the word “mixture” in the substances hierarchy is to be discouraged, since as a general scope statement, SNOMED CT does not include combination substances that are a mixture of more than one individual chemical even when the two exhibit a synergistic effect, e.g., tazobactam and piperacillin.

Changes to SNOMED CT concept model in the future to permit the use of concepts within the products hierarchy to model disorder and findings concepts means that these combined substances concepts will no longer be required, and so, will be inactivated at that time.

The scope of substances in SNOMED CT is broader than that of IDMP, since the definition of regulated products is not the only use case supported by the SNOMED CT substances hierarchy.

IDMP classes are used to identify which features could/should be identified as defining. This is different from the SNOMED CT requirement to identify top level concepts to support a hierarchy that provides a logical structure for substance concepts.

IDMP makes a distinction between Substance and the more closely defined Specified Substance. Substances are “any matter of defined composition that has discrete existence, whose origin may be biological, mineral or chemical".

1. Specified Substances are "defined by groups of elements that describe multi-substance materials or specifies further information on substances relevant to the description of Medicinal Products".

2. Specified substances include mixture substances, substances defined by pharmacopoeial specification or substances where a particular manufacturing process is specified.

In order for SNOMED CT to support the IDMP work, whose primary goal is to define unambiguously all substances present in regulated products, it is necessary for both the concepts that are IDMP Substances and those that are IDMP Specified Substances to be present in the SNOMED CT Substance hierarchy. Stereoisomers, hydrates, and solvates are included in the SNOMED CT substances hierarchy as concepts, as well as concepts to represent their base chemical in the SNOMED CT substance hierarchy. Since both IDMP Substances and IDMP Specified Substances are candidate concepts to be used in the ingredient role attributes, it does not add value in the definition of these concepts to separately identify IDMP Substances and IDMP Specified Substances in SNOMED CT and would likely cause confusion where substance concepts are used to define concepts outside the scope of IDMP and the medicinal product hierarchy.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Overview

Groupers based on disposition that are deemed to be clinically useful and that can be sufficiently defined will be included in the |Substance| hierarchy. Disposition is defined as a behavior that a substance will exhibit or participate in, given the appropriate context. There is no requirement to introduce a new semantic tag in order to distinguish concepts representing a substance disposition from any other type of concept in the |Substance| hierarchy.

Note: This section applies to concepts representing a single disposition. It does not apply to concepts representing a disposition combined with a structural grouper or concepts representing more than one disposition.

Modeling

Substance groupers representing etiopathic dispositions (e.g. 88376000 |Carcinogen (substance), 45986006 |Teratogen (substance)) will be created. Since most substances can exhibit these characteristics in some circumstances, the descendant concepts will not be populated. Exceptions will be noted in the editorial guidelines.

The following illustrates the stated view for grouper concepts based on disposition.

The following illustrates the inferred view for grouper concepts based on disposition.

Use the following pattern for the FSN. The FSN must reflect the terming used to describe the disposition consistent with the terming of the |Has disposition| attribute value.

Example for dispositions that represent a mechanism of action:

• Substance with opioid receptor agonist mechanism of action (substance)

• Substance with histamine receptor antagonist mechanism of action (substance)

• Substance with acetylcholinesterase inhibitor mechanism of action (substance)

Use the following pattern for the Preferred Term. The Preferred Term must reflect the terming used to describe the disposition consistent with the terming of the |Has disposition| attribute value.

Example for dispositions that represent a mechanism of action:

• Opioid receptor agonist

• Histamine receptor antagonist

• Acetylcholinesterase inhibitor

Synonyms corresponding to the FSN are not required.

Additional synonyms are allowed only if they are consistent with the synonyms for the corresponding disposition concept.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Overview

Groupers based on both structure and disposition that are deemed to be clinically useful and that can be sufficiently defined will be included in the |Substance| hierarchy.

Note: This section applies to concepts representing a single structural parent and a single disposition. It does not apply concepts representing more than one structural parent or disposition.

Modeling

The following illustrates the stated and inferred view for grouper concepts based on both structure and disposition.

Use the following pattern for the FSN, with X representing the structure and Y representing the disposition. The FSN should align with the FSN for the substance grouper and disposition used as the stated parent and attribute value respectively.

• X with Y mechanism of action (substance)

For example,

• Piperazine derivative with histamine H1 receptor antagonist mechanism of action (substance)

• Substance with dihydropyridine derivative structure and calcium channel blocker mechanism of action (substance)

• Substance with organophosphorus structure and acetylcholinesterase inhibitor mechanism of action (substance)

Use the following pattern for the Preferred Term, with X representing the structure and Y representing the disposition. The FSN should align with the FSN for the substance grouper and disposition used as the stated parent and attribute value respectively.

• X Y

For example,

• Piperazine derivative histamine H1 receptor antagonist

• Dihydropyridine derivative calcium channel blocker

• Organophosphorus acetylcholinesterase inhibitor

A synonym to match the FSN is not required.

Additional synonyms are allowed only if they are consistent with the synonyms for the corresponding structure grouper and disposition.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

In the SNOMED CT substance hierarchy, there are a large number of grouper concepts. Currently, groupers within the substances can be considered to be structural groupers, disposition groupers, or role based.

The intent is to build the SNOMED CT substance hierarchy along structural or disposition groupers and use a |Has disposition (attribute)| relationship to define grouper concepts in the substance hierarchy. Grouper concepts that do not reference structural or disposition properties of a substance should not be included within the substance hierarchy and existing role concepts are considered for relocation outside of the substance hierarchy.

Groupers that organize substances by their chemical structure are used as the main hierarchy for substances. Where substances are heterogeneous and do not have a single identifiable chemical structure, such as those of biological origin, it may be more appropriate to organize them by source.

In the context of substances, a disposition is “a behavior that a substance will exhibit or participate in, given the appropriate context.” This context-based definition of disposition would allow us to assign |Has disposition (attribute)| values that are necessarily true, even though the substance does not exhibit the disposition in all contexts.

Role based groupers are associated with a particular purpose or outcome. Roles are a function of the way the substance is formulated or presented and so may not be applicable to all products containing that substance, which may lead to incorrect classification of concepts using role groupers as attribute values. At this time, the existing Substance role groupers will remain in situ with no change. However, additional concepts of this type will not be created, and requests for new instances will be rejected.

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Overview

Groupers based on structural properties of the substance that are deemed to be clinically useful will be included in the Substance hierarchy.

For example,

• Benzodiazepine (substance)

• Quinolone (substance)

Modeling

The following illustrates the stated and inferred view.

Use the following pattern for the FSN. Groupers are expressed in the singular, i.e., compound not compounds.

Examples of substances that represent a structural grouper:

• Organic nitrogen compound (substance)

• Halide compound (substance)

• Triazine derivative (substance)

• Copper and/or copper compound (substance)

Where the same word is used to identify both a group of substances with a particular chemical structure and a particular chemical substance, the following terming for the FSN is used for the substance grouper concept.

Substance with X structure (substance)

For example,

• Substance with tetracycline structure (substance)

• Substance with cresol structure (substance)

• Substance with benzene structure (substance)

Use the following pattern for the Preferred Term.

For example,

• Organic nitrogen compound

• Halide compound

• Triazine derivative

• Copper and/or copper compound

Where the same word is used to identify both a group of substances with a particular chemical structure and a particular chemical substance the following pattern will be used for PT the substance grouper concept.

Substance with X structure

For example,

• Substance with tetracycline structure

• Substance with cresol structure

• Substance with benzene structure

Additional synonyms are not allowed unless explicitly identified as an exception in the editorial guidelines.

Browser view of 299979007 |Organic nitrogen compound (substance)|

Browser view of 767209009 |Copper and/or copper compound (substance)|

Browser view of 766224008 |Substance with cresol structure (substance)|

This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.

Overview

The substance redesign project has made a number of decisions regarding the representation of a substance and its modifications.

1. Modification indicates that the concept is a structural modification of another concept, where the intrinsic physicochemical properties of the substance do not change.

2. The intrinsic physicochemical properties do not encompass non-intrinsic characteristics of a substance, such as toxicity, bioavailability, or extended release (in the case of medicinal products).

3. Modification concepts that exist to group modifications or derivatives of a specific substance are not to be created.

4. Metabolite groupers in the substances hierarchy are considered roles. No further concepts of this format will be created in the |Substance| hierarchy. Existing concepts will only be retained where there is a specific requirement and will be modeled as a child of |Metabolite (substance)|. See .

5. Structural groupers that reference modifications as a chemical group will be retained. Where the structural group name also refers to a specific chemical, the grouper will be re-termed “Substance with X structure”. See relative section .

6. There is no requirement to introduce a new semantic tag in order to distinguish concepts representing a substance or its modifications from any other type of concept in the |Substance| hierarchy.

The following illustrates the stated view of 125691000 |Sotalol hydrochloride (substance)|:

The following illustrates the inferred view for 125691000 |Sotalol hydrochloride (substance)|:

Substances may have zero to many |Is modification of attribute|(s).

• For example,

  • Morphine hydrochloride (substance)

• For example,

  • Fluorothymidine (18-F) (substance)

Hydrates have an 738774007 | Is modification of (attribute)| relationship to the unspecified salt.

• For example,

  • Caffeine hydrate (substance) IS MODIFICATION OF Caffeine (substance).

This is the stated view:

This is the inferred view:

For example,

• Clindamycin hydrochloride monohydrate (substance) IS MODIFICATION OF Clindamycin hydrochloride (substance).

This is the stated view:

This is the inferred view:

For example,

• Calcium lactate pentahydrate (substance) IS MODIFICATION OF Calcium lactate (substance)

This is the stated and inferred view.

Anhydrous salts have an 738774007 | Is modification of (attribute)| relationship to the unspecified salt.

• For example,

  • Theophylline anhydrous (substance) IS MODIFICATION OF Theophylline (substance).

This is the stated view:

This is the inferred view:

The salts are modeled with an 738774007 | Is modification of (attribute)| the acid substance.

• For example,

  • Pamidronate monosodium (substance) IS MODIFICATION OF Pamidronic acid (substance). This is the stated and inferred view.

Liposomal preparations are modifications of the chemical substance.

• For example,

  • Daunorubicin citrate liposome (substance)|

Pegylated substances are modeled with |s modification of (attribute)| generic substance, if such a substance has been made available. Not all pegylated medicinal substances have a non-pegylated form, as the non-pegylated form may have been too immunogenic or too toxic.

• For example,

  • 785674001 |Turoctocog alfa pegol (substance)|

Concepts specifying a particular physical form (e.g., micronized, macrocrystal, microsphere) should have a parent concept that relates to the structure of the substance and also an |Is modification of (attribute)| relationship to the unspecified substance concept.

• For example,

  • 414246008 |Fenofibrate micronized (substance)|

Grouper concepts should not be targets of an 738774007 | Is modification of (attribute)| relationship.

In general, an 738774007 | Is modification of (attribute)| is not applicable to prodrugs. This is because there is no requirement for the |Has active ingredient (attribute)| of medicinal products containing prodrug substances to use any relationship to the active substance to manage relationships within the medicinal product hierarchy.

For example, aspirin is not generally considered a modification of the substance salicylic acid.

738774007 | Is modification of (attribute)| is not applicable:

• Between a glycan and its glycoconjugate.

  • For example, 259289005 |Trimethylene glycol (substance)| is not a modification of 52086008 |Glycol (substance)|.

• To genetic engineering process variations (e.g., Somatropin(epr), Somatropin(rbe), or Somatropin(rmc)), as SNOMED CT does not generally differentiate substances based on production process.

• Between a chemical element and its salt.