> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/snomed-ct-specifications/snomed-ct-editorial-guide/readme/authoring/domain-specific-modeling/substance.md). # Substance
DefinitionExamples

The |Substance| hierarchy contains concepts that can be used for recording and modeling: chemical constituents of medicinal and non-medicinal products; allergies, adverse reactions, poisoning; physicians and nursing orders and laboratory reports and results.

Subhierarchies of |Substance| include but are not limited to |Body substance (substance)| and |Chemical (substance)|

  • Albumin (substance)
  • Amoxicillin (substance)
  • Amoxicillin trihydrate (substance)
  • Chromatin (substance)
  • Endorphin (substance)
  • Methane (substance)
  • Paracetamol (substance)
## General Assumptions and Requirements Scope of the |Substance| hierarchy in the International Release include substances that support the modeling of concepts in other SNOMED CT hierarchies, such as Medicinal product, Clinical finding, Procedure, Observable Entity, and Specimen. Decisions regarding requirements, applicable use cases, scope, terming, and modeling guidelines are made based on requests submitted by user community and in consultation with subject matter experts, associated Project Groups, and relevant credible references. Top level concepts in the hierarchy will primarily be grouper concepts for both the stated and inferred views. Concepts representing dispositions in the |Substance| hierarchy shall be sufficiently defined using proximal primitive modeling methodology unless explicitly noted as an exception in the editorial guidelines. ## Out of scope Concepts describing the following are out of scope for the Substance hierarchy. ### Dose form or Route of administration Concepts that refer to dose form (e.g., solution) or route of administration (e.g., topical) * Existing instances will be inactivated as nonconformant to editorial policy. Requests for new instances will be rejected. ### Role or Context Concepts that refer to role or a specific context (e.g., dietary, medicinal, non-pharmaceutical, substance of abuse) * Existing instances will be kept in the substance hierarchy; however, additional concepts of this type will not be created, and requests for new instances will be rejected. ### Release state Concepts that refer to a release state (e.g., immediate release, extended release) * Existing instances will be inactivated as nonconformant to editorial policy. Requests for new instances will be rejected. ### Brand or trade name Concepts that refer to a brand or trade name * Existing instances will be inactivated as nonconformant to editorial policy. Requests for new instances will be rejected. ### Base and total descriptions Concepts that state *total* due to the inability to differentiate the definition between the *base* substance and *total* substance (e.g., *cholesterol* versus *total cholesterol*) as well as the inability to create an appropriate relationship between the *base* and *total* concepts * Existing instances will be inactivated as nonconformant to editorial policy. Requests for new instances will be rejected. ### Homeopathic products Substances used in homeopathic products * Existing instances will be retained for now; however, requests for new instances will be rejected. ### Traditional medicine products Substances used in traditional medicine products * Existing instances will be retained for now; however, requests for new instances will be rejected. ### Combinations and mixtures Concepts that represent a combination of two or more separate substances * Existing instances have been inactivated. Changes to SNOMED CT concept model to permit the use of concepts within the products hierarchy (e.g., vaccine products) as well as use of General Concept Inclusion functionality to model disorder and findings concepts means that combined substances concepts are no longer required. Requests for new instances will be considered on a case-by-case basis. Substances that identify a mix of allergens to be tested for allergy reporting are excluded from SNOMED CT. These tests are considered ambiguous when they do not specify the specific allergens being tested. * For example, * Immunoglobulin E antibody to mold mix (substance) #### EXCEPTIONS Combined dried gels, also known as co-dried gels, are registered as a single "substance" (or a Specified Substance) in the IDMP database, rather than two separate substances. Because the structural modification creates a unique chemical entity with different properties than the sum of its parts, regulators treat it as its own unique ingredient. * For example, * 380671000087102 |Aluminium hydroxide magnesium carbonate co-dried gel (substance)| Due to the nature of some natural medicines, regulations regarding strength expression of individual components differ to conventional medicines, and strength may be expressed as a combination of the active ingredients. Whilst equivalence can be modeled in SNOMED CT, the combined strength cannot (as the strength of the individual components is not expressed); therefore, a combined substance is permitted that represents the individual components. * For example, * Sennoside A and B can have an expressed strength of "12mg or equivalence (expressed as Sennoside B)" * Calcium sennosides can have an expressed strength of "calcium sennosides equivalent to 7.5 mg per 5 ml total sennosides (calculated as sennoside B) ### Genetic engineering process variations Concepts representing genetic engineering process variations such as Somatropin (epr), Somatropin (rbe), or Somatropin (rmc) are out of scope as SNOMED CT does not generally differentiate substances based on production process. * Existing instances will be inactivated. Requests for new instances will be rejected. Provide Feedback --- # Agent Instructions This documentation is published with GitBook. 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