Many extracted substances in SNOMED CT are not specific to either the part of the plant (root, seed, leaf, etc.) or the form (powder, dry or soft extract, etc.). The specific part of the plant should be known and documented when using these substances in modeling medicinal products. The less specific descriptions may find use in hierarchies besides Pharmaceutical / biologic product (product), such as the need to record an adverse reaction to a substance where the full details are unknown. While the most specific information is encouraged, all levels of specificity can be represented in SNOMED CT.

Naming pattern:

FSN: [Scientific name of source organism] <part of plant> extract (substance)

PT: [Common name of organism] <part of plant> extract

SYN: [Scientific name of source organism] <part of plant> extract

Extracts that include form

For extracts that include form (such as dry), the form should follow the source in the FSN and the corresponding SYN. The PT can have the form either in front of or following the source, whichever is prevailing in the literature.

• For example,

  • FSN: Betula dry extract (substance)

  • PT: Dry birch extract

Preferred references for plant scientific and common names include the following:

• Integrated Taxonomic Information System

• Catalogue of Life

Thermo Fisher Scientific may be consulted for allergens.

The Global Substance Registration System (GSRS) is a good resource for substance names (INN, chemical names) but not necessarily the best for synonyms.

Some requests are for extracts of which the genus is too broad, while the requirement for the species is too specific. In these cases, the common name can be used; a scientific name is not used.

• For example,

  • If the requested concept is for blueberry extract, there is no single genus and species that identifies the blueberry plant. The Vaccinium genus includes cranberry, ligonberry, and other berry plants in addition to blueberry. There are multiple blueberry species. Therefore, the concept can be created for blueberry extract without a scientific name. The common name has a case sensitivity indicator of ci.

See related section at

Though an extract is derived from a substance, it is not a type of that substance.

• For example,

• |Ginkgo biloba extract (substance)| would not have a parent of |Ginkgo biloba (substance)|.

Ribonucleic acid of X organism

Modeling

Pattern:

• Ribonucleic acid of X organism (substance)

For example,

• Ribonucleic acid of Norovirus genogroup I (substance)

Preferred Term (US/GB) with initial letter case sensitive:

Pattern:

• X organism RNA

For example,

• Norovirus genogroup I

Pattern: A synonym that matches FSN

For example,

• Ribonucleic acid of Norovirus genogroup I

Additional synonyms (when a legitimate synonym exists for Organism name) are applicable.

The following illustrates the stated and inferred view:

Pattern:

• Ribosomal ribonucleic acid of X organism (substance)

For example,

• Ribosomal ribonucleic acid of Candida (substance)

Preferred Term, with Initial letter case sensitive.

Pattern:

• X organism rRNA

For example,

• Candida rRNA

Pattern:

• A synonym that matches FSN

For example,

• Ribosomal ribonucleic acid of Candida

Additional synonyms (when a legitimate synonym exists for Organism name) are applicable.

The following illustrates the stated and inferred view:

Pattern: Messenger ribonucleic acid of X organism (substance)

For example,

• Messenger ribonucleic acid of Severe acute respiratory syndrome coronavirus 2 (substance)

Preferred Term, with Initial letter case sensitive.

Pattern: X organism mRNA

For example,

• SARS-CoV-2 mRNA

Pattern: A synonym that matches FSN

For example,

• Messenger ribonucleic acid of Severe acute respiratory syndrome coronavirus 2

Additional synonyms (when a legitimate synonym exists for Organism name) are applicable.

Stated and inferred view of 1119343008 |Messenger ribonucleic acid of severe acute respiratory syndrome coronavirus 2 (substance)|:

Pattern: Messenger ribonucleic acid of X organism encoding for protein Y (substance)

For example,

• Messenger ribonucleic acid of Severe acute respiratory syndrome coronavirus 2 encoding spike protein (substance)

Preferred Term, with Initial letter case sensitive.

Pattern: X organism mRNA encoding for protein Y

For example,

• SARS-CoV-2 mRNA encoding spike protein

Pattern: A synonym that matches FSN

For example,

• Messenger ribonucleic acid of Severe acute respiratory syndrome coronavirus 2 encoding spike protein (substance)

Additional synonyms (when a legitimate synonym exists for Organism name) are applicable.

Stated and inferred view of 1155866009 |Messenger ribonucleic acid of severe acute respiratory syndrome coronavirus 2 encoding spike protein (substance)|:

Pattern: Deoxyribonucleic acid of X organism (substance)

For example,

• Deoxyribonucleic acid of Aspergillus terreus (substance)

Preferred Term (US/GB), with Initial letter case sensitive:

Pattern: X organism DNA

For example,

• Aspergillus terreus DNA

Pattern: A synonym that matches FSN

For example,

• Deoxyribonucleic acid of Aspergillus terreus

Additional synonyms (when a legitimate synonym exists for Organism name) are applicable.

The following illustrates the stated and inferred view:

Overview

Substance concepts should, where possible, be modeled with either a structural parent or one that denotes source or origin.

Modeling

FSN, PT or Synonym should not contain "- dietary" context in descriptions

FSN, PT or Synonym should not contain brand or trade names.

Culinary name should be used for the FSN and PT when referring to meat products and food, e.g., Beef dripping (substance), Pork sausage (substance).

If there are additional adjectives such as baked, boiled, fried, lean, minced, low-fat, roast, or stewed, these adjectives should proceed the name of source organism, e.g., Fried beef steak (substance), Tinned fish (substance).

Pattern:

• X (substance)

For example,

• Betel nut (substance)

• Wheat dextrin (substance)

• Tinned fish (substance)

Pattern:

• X

For example,

• Betel nut

• Wheat dextrin

• Tinned fish

Pattern: scientific name if appropriate

For example,

• Areca catechu

The following illustrates the stated and inferred view.

The following illustrates the stated and inferred view.

Overview

Concepts specifying a particular physical state (e.g. liquid, solid, fumes, vapor, crystal, foam) of a substance should be represented as the sibling for the unspecified substance and also have a parent concept that relates to the structure of the 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.

Modeling - Micronized substance

Fumes should be expressed in the plural (i.e. fumes as opposed to fume).

Fumes and vapor are different and so should not be used as synonyms on the same concept.

Pattern:

• X fumes (substance)

• X micronized (substance)

For example,

• Bauxite fumes (substance)

• Fenofibrate micronized (substance)

Pattern:

• X fumes

• X micronized

For example,

• Bauxite fumes

• Fenofibrate micronized

Pattern: X form to represent EN-GB language variants where appropriate

For example,

• Fenofibrate micronised

View of both stated and inferred form of 278945005 |Iron fumes (substance)|:

Stated view of 414246008 |Fenofibrate micronized (substance)|:

Overview

This section includes concepts that represent flap substances used in flap surgery. The concepts in this subhierarchy are used to define:

Flap composition

• For example,

  • bone, skin, muscle, myocutanous, osteocutaneous

Flap blood supply

• For example,

  • Free flap: A completely detached flap transferred with its own blood supply intact is known as a free flap. A free flap is re-attached at the recipient site, which is a highly skilled technique, often involving microsurgical anastomosis of the blood vessels

  • Pedicle flap: A pedicle flap is transferred still attached to its original blood supply (the pedicle)

Flap substances exist for free flaps and pedicle flaps (<<261238005 |Free flap (substance)| and << 261235008 |Pedicle flap (substance)|) and reflect the fact that whether a flap is free or pedicle is also a function of its blood supply (i.e. completely unattached from its original blood supply, or still attached via a vascular pedicle).

Flap substances comprising composite multiple flap tissues are siblings (and not subtypes) of the various single tissue flap substances from which they are composed.

Flap substances should not include the procedure method, such as whether a flap is local or distant, or if a flap is rotated or advanced.

The concepts in this subhierarchy must not be conflated with either the donor procedure site or the site that the procedure acts upon.

For substances representing skin flaps, the FSN and PT contains ‘skin flap’ with an acceptable synonym of ‘cutaneous flap’.

For osteocutaneous flaps, terming for FSN and PT is ‘osteocutaneous flap’ with an acceptable synonym of ‘osseocutaneous flap’.

Creation of substance concepts that contain “bound” is limited to the measurement of biological substances (Observable entities, evaluation procedures, LOINC collaboration project) or to report their level (clinical findings).

Where the substance is "bound" the molecule to which the substance is bound to may be specified in the term.

Overview

A metabolite is a substance created or utilized during metabolism, the process by which the body breaks down food, drugs, chemicals, or its own tissues (e.g., fat, muscle). Metabolites are differentiated from derivatives, that are compounds synthesized by modifying precursor compounds and are important in discovery of new drugs (e.g., molecules with improved efficacy, reduced toxicity, or enhanced pharmacokinetic profiles), materials science (e.g., polymers with altered properties), and agrochemicals (e.g., potent pesticide).

Concepts representing Metabolites of X will be considered for inclusion based upon project requirements.

Modeling

Pattern: X metabolite (substance)

For example,

• Cocaine metabolite (substance)

Pattern: X metabolite

For example,

• Cocaine metabolite

The following illustrates the stated and inferred view:

This section of the document provides guidance for specific types of substances.

• Antibodies and antigens

• Antivenom

• Autoantibody

Overview

Creation of substance concepts that contain terms such as “free” (or "unbound" or "unconjugated") is limited to the measurement of biological substances (Observable entities, evaluation procedures, LOINC collaboration project) or to report their level (clinical findings). These concepts are created as siblings of the base concepts with a "substance X and X derivatives" or "X and X compound" as common supertype.

Modeling

Pattern: Free X (substance)

For example,

• Free iodine (substance)

Pattern: Free X

For example,

• Free iodine

Optional pattern: Unbound x

For example,

• Unbound iodine

The following illustrates both the stated and inferred view:

The following illustrates the hierarchy view:

Overview

A recombinant (A new entity e.g., gene, protein, cell, or individual that results from genetic recombination) or synthetic/semi-synthetic substance (of, relating to, or produced by chemical or biochemical synthesis; especially: produced artificially) is similar in structure (but not identical to the naturally occurring substance). It should be created as a sibling of the naturally occurring substance.

A substance that is part of (e.g. dander) or is derived from (e.g. Insulin) an organism (human or non-human) is identical and should be created as a child of the naturally occurring substance.

Modeling

“Recombinant”, “Synthetic”, or “Semi-synthetic” should precede the name of the substance

The source organism name should precede the name of the substance

• An exception to this rule is the naming of DNA, RNA, rRNA, antibody, Immunoglobulin, and antigen of organisms, which should follow the guideline specified for antibodies and antigens

• For some non-human sources, there are different ways of referring to the source organism:

  • The common name of the organism e.g. pig, cow, horse, mouse, sheep

Additional adjectives (such as labeled, Iodinated) should proceed the name of source organism

• For example,

  • Lente human insulin (substance)

  • Iodinated (125-I) human serum albumin (substance)

If a concept includes “recombinant” or “synthetic” as well as a source organism, “recombinant” or “synthetic” should precede the source organism name

• For example,

  • Recombinant bovine growth hormone (substance)

Pattern:

• [Source organism] X (substance)

• Recombinant X (substance)

• Synthetic X (substance)

For example,

• Human antithrombin III (substance)

• Recombinant thrombin (substance)

• Synthetic steroid (substance)

Pattern:

• [Source organism] X

• Recombinant X

• Synthetic X

For example,

• Human antithrombin III

• Recombinant thrombin

• Synthetic steroid

The naming of DNA, RNA, rRNA, antibody, Immunoglobulin, and antigen of organisms should follow the specific guideline for this type of substances.

Stated view of 411973001 |Bovine thrombin (substance)|

Overview

Acids substance concepts should be modeled with a structural parent concept.

Salts should be modeled with a conjugate base as parent (if one exists, otherwise they are modeled with a structural parent). Salts may have an Is modification of (attribute) relationship to the conjugate acid where a specific use case is identified. See examples of such use cases at Concepts Representing a Substance or its Modifications.

Conjugate base concepts (e.g., valproate, pamidronate, etidronate) should only be created where a specific use case is identified, for example, when required to support the definition of other concepts in the terminology.

Conjugate bases should be created as separate concepts - not added as synonyms to the corresponding acid concept.

New instances of substance concepts containing the word salt will not be added. The existing concepts will be reviewed, and if possible, will be replaced by equivalent compounds.

Modeling

Where INN names exist, these should be used for the FSN and PT.

Pattern:

• X sulfate (substance)

• X pamidronate (substance)

For example,

• Copper sulfate (substance)

• Disodium pamidronate (substance)

• Etidronate (substance)

Exception:

• Valproate sodium (substance)

Pattern:

• X sulfate

• X pamidronate

For example,

• Copper sulfate

• Pamidronate monosodium

• Etidronate

Exception:

• Valproate sodium

Pattern: Pamidronate X

For example,

• Pamidronate monosodium

• Valproate sodium

Stated view of 387080000 |Valproic acid (substance)|:

Stated and inferred view of 387481005 |Sodium valproate (substance)|:

Hierarchy view of 264325000 |Valproate (substance)| subtypes:

The following illustrates the stated and inferred views.

Modeling

Hydates are modeled with an 738774007 | Is modification of (attribute)| relationship to the substance with unspecified hydration.

For example,

• Ferrous oxalate dihydrate (substance) is modification of → Ferrous oxalate

• Caffeine hydrate (substance) is modification of → Caffeine

• Zinc sulfate heptahydrate (substance) is modification of → Zinc sulfate

Pattern:

• X hydrate (substance)

• X dihydrate (substance)

• X monohydrate (substance)

For example,

• Copper sulfate pentahydrate (substance)

Pattern:

• X hydrate

• X dihydrate

• X monohydrate

For example,

• Copper sulfate pentahydrate

The following illustrates the inferred view.

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

Anhydrous compounds have an 738774007 | Is modification of (attribute)| relationship to the unspecified substance, i.e., where the level hydration is not specified.

For example,

• Sodium carbonate anhydrous (substance) is modification of → Sodium carbonate

• Theophylline anhydrous (substance) is modification of → Theophylline

Pattern:

• X anhydrous (substance)

For example,

• Theophylline anhydrous (substance)

Pattern:

• X anhydrous

For example,

• Theophylline anhydrous

Anhydrous X

The following illustrates the inferred view.

|Theophylline anhydrous (substance)| IS MODIFICATION OF |Theophylline (substance)|

Modeling

Saturated X (substance)

Unsaturated X (substance)

For example,

• Unsaturated adipate (substance)

Saturated X

Unsaturated X

For example,

• Unsaturated adipate

X Saturated or X Unsaturated

For example,

• Adipate unsaturated

The following illustrates the stated and inferred view:

Fragments are created as siblings of the intact/whole/entire substance.

“Intact” should not be included when referring to the "entire substance" or "whole substance"; it is implied.

Alpha and beta sub-units should be the children of the entire substance, where "nicked" substances and fragments should be the siblings.

INN should be used for the Preferred Term where they exist.

Modeling

Pattern: "Antibody to" + Antibody target

Note: An antibody target can be an antigen or another antibody.

For example,

• Antibody to nuclear antigen (substance)

• Antibody to thyroglobulin immunoglobulin G (substance)

Pattern: Antibody target + "antibody"

For example,

• Nuclear antibody or Thyroglobulin immunoglobulin G antibody

Pattern: A synonym that matches FSN

For example,

• Antibody to nuclear antigen

• Antibody to thyroglobulin immunoglobulin G

Pattern: Antibody target + "Ab"

For example,

• Nuclear Ab

• Thyroglobulin IgG Ab

Additional synonyms:

• Add a description containing antibody target + "autoantibody"

  • Nuclear autoantibody

  • Thyroglobulin IgG autoantibody

Previously, SNOMED CT represented ions and electrolytes as separate concepts. Although the two terms are subtly different, there is considerable overlap in their definitions, and they seem to be used interchangeably in medicine. The Substances Redesign Project Group considered this issue and determined the following:

• Ions should be modeled as child concepts of the substance.

• A second parent (in addition to X (substance)), that indicates the concept is an ionized substance, should be modeled.

Overview

Substance concepts that contain terms such as “fractionated” or “unfractionated” are not created in the Substance hierarchy. "Unfractinated" should not be included when referring to the "entire substance" or "whole substance"; it is implied. "Fractionated" usually refers to a separation technique or process.

Provide Feedback

Overview

This section includes concepts that represent

• Antigen of organism

• Antibody to organism

• Immunoglobulin G, M, A, E, D antibody to organism

Organism above includes substances derived from an organism, for example, feather or protein.

When referring to an organism name, while the Linnean taxon ranks (such as genus) are not included, the subspecies variants (such as biotype and serotype) are included in the naming. This avoids ambiguity when the same number or letter is used to refer to different organism variants.

• For example,

  • Without mentioning the specific variant (serogroup vs. serotype) and the nomenclature system (Danish vs. American), Streptococcus pneumoniae 48 can refer to the following:

    • Streptococcus pneumoniae Danish serotype 48 (which is equivalent to Streptococcus pneumoniae American serotype 82)

The antigen name is usually derived from the biological name of the organism as opposed to the disease or infection that the organism may cause and/or that the vaccine may provide immunization for.

Pattern:

• Antigen of X organism (substance)

For example,

• Antigen of Filaria (substance)

• Antigen of Alternaria alternata protein (substance)

Pattern:

• X organism antigen

For example,

• Filaria antigen

• Alternaria alternata protein antigen

Exception:

• Preferred term for |Antigen of live attenuated Mycobacterium bovis| is |Bacillus Calmette-Guerin antigen|

1. Pattern: A synonym that matches FSN

   1. For example,

      1. Antigen of Filaria

There is a requirement for the inclusion of characteristic technologies that are essential for distinguishing between different antigen variants that are used in manufacturing vaccine products, e.g., live attenuated, inactivated, or subunit antigens. Antigen variants are evaluated for:

• References such as WHO, CDC, UpToDate, vaccine package inserts

• Inclusion in the international release vs. national extensions

• Hierarchy they belong to: Substance or Product

To prevent the creation of transient or short-lived viral strain content, the International Release will not create specific viral variant strains or their corresponding antigen substance concepts when those variants have only brief or limited existence. For the purpose of defining clinical drugs or vaccine products in the International Release, stable higher-level parent virus or antigen concepts should be used instead. National Release Centers (NRCs) that require representation of specific viral variants for local regulatory or clinical use cases may create such concepts within their extensions.

"Antigen of X" is in scope for the international release and is modeled in the Substance hierarchy. It is a generic grouper concept and subsumes all instances of antigen variants related to Organism X.

• X refers to a bacteria, virus, fungus, or parasite except when antigen refers to the organism “toxin/toxoid”, where it can only apply to a bacteria.

“Antigen of live attenuated X” is in scope for the international release and is modeled in the Substance hierarchy as a direct child of |Antigen of X|.

• It refers to attenuated whole cell bacteria or whole virus where the strains are made less virulent so infection is usually inapparent or very mild. It may be used in the creation of vaccine products for certain patient groups, and hence, is of clinical significance.

• The following subtypes are also in scope for the international release and are modeled in the Substance hierarchy as direct children of |Antigen of live attenuated X|. In the following examples, human and bovine refer to source organisms which are differentiated from the organism producing antigen, i.e., Rotavirus.

  • “Live attenuated human X”, e.g., Antigen of live attenuated human Rotavirus serotype G1P[8]

“Antigen of inactivated whole X” is in scope for the international release and is modeled in the Substance hierarchy as a direct child of Antigen of X.

• It refers to the killed version of the organism that causes a disease.

• As of the July 2020 release, the word "whole" is added to all new and existing concepts referring to "Antigen of inactivated X" to further clarify the differentiation between "Antigen of inactivated whole organism" (referring to a killed organism as a whole) and "Antigen of organism [subunit]" (referring to subparts of an organism).

“Antigen of acellular X” is in scope for the international release and is modeled in the Substance hierarchy as the direct child of "Antigen of X".

• "Antigen of acellular X", when it exists, can only apply to a bacteria.

“Antigen of X [subunit]” is in scope for the international release and is modeled in the Substance hierarchy as the direct child of “Antigen of X”.

• Subunit antigens differ from inactivated whole-cell antigens by referring only to the antigenic parts of the pathogen. These parts are necessary to elicit a protective immune response. The word “inactivated” does not need to be part of the name unless it is referring to a whole cell or a whole virus, i.e., for descriptions referring to a subunit, the word inactivated will be omitted as redundant.

• [Subunit] refers to a sub-part of an organism i.e. a specific, isolated protein of the pathogen, a recombinant protein (made by recombinant DNA techniques), an inactivated toxin (toxoid), or a capsular polysaccharide/oligosaccharide coating of an encapsulated bacterium:

  • "Antigen of X [protein/recombinant protein]" is in scope for the international release and is modeled in the Substance hierarchy.

When referring to Organism parts/subunits:

• Referring to more than one subunit (e.g., combined protein such as Bordetella pertussis FIM 2 and FIM 3 antigen) would not be acceptable for the Substance hierarchy; the combined protein needs to be modeled at the product level with more than one active ingredient.

• Abbreviated organism subunit names such as "Corynebacterium diphtheriae CRM197 protein", are not allowed in a fully specified name (and similar synonym). The FSN and similar synonym should only include the spelled-out terms, i.e., "Corynebacterium diphtheriae cross-reacting material 197 protein".

• Abbreviated organism part names are allowed in a preferred term (and other synonyms). The abbreviations do not need to be accompanied by the fully expanded term, which is an exception to the general naming guidelines on abbreviations and acronyms in the SNOMED CT Editorial Guide.

Inclusion of vaccine manufacturing techniques and/or residuals in antigen names is generally out of scope for the international release. However, exceptions can be made for applicable use cases.

• "Antigen of X grown in nervous tissue" or "Antigen of X grown in cellular line" is acceptable for inactivated Rabies antigens grown in brain tissue or cell lines and is included in the international release, considering the difference in the adverse reactions that they cause. If and when created:

  • "Antigen of X grown in cellular line" will be a grouper and other subgroups will be added as needed, e.g., "grown in Human diploid cell".

  • "Antigen of X grown in nervous tissue" should indicate the specific type of nervous tissue, e.g., brain.

• Antigen of X

  • Antigen of live attenuated X

  • Antigen of inactivated whole X

The following illustrates the stated and inferred view:

Pattern:

• Antibody to X organism (substance)

For example,

• Antibody to Bebaru virus (substance)

Pattern:

• X organism antibody

For example,

• Bebaru virus antibody

1. Pattern: A synonym that matches FSN

   1. For example,

      1. Antibody to Bebaru virus

Additional synonyms (e.g., when a legitimate synonym exists for Organism name, such as common names) are applicable.

The following illustrates the stated and inferred view:

Pattern:

• Immunoglobulin G, M, A, E, D antibody to X organism (substance)

For example,

• Immunoglobulin M antibody to Clostridium difficile (substance)

• Immunoglobulin G antibody to Juglans (substance)

Pattern:

• X organism IgG, M, A, E, D

For example,

• Clostridium difficile IgM

• Walnut IgG

  • Walnut is the common name for Juglans.

1. Pattern: A synonym that matches FSN

   1. For example,

      1. Immunoglobulin M antibody to Clostridium difficile

Additional synonyms (e.g., when a legitimate synonym exists for Organism name, such as common names) are applicable.

• For example,

  • Juglans IgG

    • Juglans is the scientific name for walnut.

The following illustrates the stated and inferred view:

Representation of radioactive isotopes

Modeling

Pattern:

• [name of isotope]-[atomic number] (substance)

For example,

• Gallium-67 (substance)

Pattern:

[name of isotope]-[atomic number]

For example,

• Gallium-67

Pattern:

• [atomic number]-[chemical symbol]

For example,

• 67-Ga

The following illustrates the hierarchy view:

The following illustrates the stated and inferred view:

Superscripts should not be used in either Fully Specified Name, Preferred Term, or synonyms.

Parentheses should be used to delineate the atomic number and chemical symbol from the rest of the terming; this aligns with INN.

Pattern: [name of isotope] ([atomic number]-[chemical symbol]) [salt] (substance)

For example,

• Gallium (67-Ga) citrate (substance

Pattern: [name of isotope] ([atomic number]-[chemical symbol]) [salt]

For example,

• Gallium (67-Ga) citrate

The following illustrates the stated and inferred view:

Superscripts should not be used in either Fully Specified Name, Preferred Term, or synonyms.

The Fully Specified Name should explicitly state that a component was “labeled” by a radioisotope in the FSN. Do not use “with”, “and”, or “tagged”.

Omit the word “labeled” from the PT; keep a synonym to match the FSN.

The following illustrates both the stated and inferred view:

Overview

Within the substances hierarchy in SNOMED CT there are a number of substances where that is either a mix of isomers of a single chemical, a racemic mix or a single isomer.

• Omeprazole and Esomeprazole

• Cetirizine and Levocetirizine

• Loratadine and Desloratadine

Each of these substances will all need to be represented in SNOMED CT as separate concepts to support the representation of active ingredients in SNOMED CT and should be represented as sibling concepts without any SNOMED CT relationship created between the two substances.

The following illustrates the hierarchy view for Omeprazole and Esomeprazole: