- Modification indicates that the concept is a structural modification of another concept, where the intrinsic physicochemical properties of the substance do not change.
- 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).
- Modification concepts that exist to group modifications or derivatives of a specific substance are not to be created.
- 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 Metabolites.
- 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 Substance Groupers Based on Structure.
- 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.
Modeling
| Semantic tag | (substance) |
|---|
| Definition status | Primitive |
|---|
Attribute: Is modification of | Range: <105590001 |Substance (substance)| |
|---|
Exemplar
The following illustrates the stated view of 125691000 |Sotalol hydrochloride (substance)|:
The following illustrates the inferred view for 125691000 |Sotalol hydrochloride (substance)|:
Guidelines for the use of 
Substances may have zero to many Is modification of attribute(s).
For example,
- Morphine hydrochloride (substance)
For example,
- Fluorothymidine (18-F) (substance)
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 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 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 relationship.
In general, an 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.
When a prodrug is an esterified form of substance, there should be an relationship between the substance and its esterified form. For exemplar,
- 715220007 |Tenofovir alafenamide (substance)|
- 89678001 |Cefuroxime axetil (substance)|
|
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.
- For example, 387307005 |Calcium carbonate (substance)| is not a modification of |Calcium (substance)|.
