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The following mapping principles were used to develop the map.

Semantic match even if characteristics/attributes are not an exact match

The map was developed , based on the principle that the source and target codes of 'equivalent' maps must be an exact semantic match.    ButHowever, the characteristics of a given PDF in Standard Terms may not exactly match the logical definition of a SNOMED CT concept, as long as the "mismatch" does not cause a semantic conflict.  Indeed in some cases the mismatch may enhance the match.  Here are some examples:

• The SNOMED CT FSN is apparently narrower than the EDQM Term based on the intended site characteristic , but is an exact match based on the definition; this usually occurs when the EDQM Term uses a grouper concept for the characteristic, whereas the SNOMED CT uses the specific concept for the attribute.
  • EDQM intended site "cutaneous/transdermal" whereas SNOMED CT has explicitly either cutaneous or transdermal as appropriate.
  • EDQM intended site "oromucosal" whereas SNOMED CT has explicitly either buccal, sublingual, etc. as appropriate.
• The SNOMED CT PDF uses a different administration method than the EDQM Term, but the difference is not considered clinically significant.
  • EDQM administration method for "rectal foam" is the very generic "administration," whereas SNOMED CT has the administration method "apply".

BUT a A characteristic/attribute mismatch must respect the semantics of the Term: for example, the EDQM PDF  PDF "oral gel" is to used for medicinal products that will be swallowed, whereas the SNOMED CT "conventional release oral gel" has an administration method of "apply" this is not appropriate since application implies use on a body surface.  (Note, this SNOMED CT concept is currently subject to a change request to resolve this and allow a semantic match. )

For more information on the semantic representation of codes in the source and target terminologies, please refer to 4.1 The Semantics of the Source and Target Dose Forms.

Matching the granularity of PDF description

Several groups of EDQM PDFs are have greater granularity than the similar dose forms used in the definition of clinical drugs in the SNOMED CT International edition.   In order to give provide a good semantic match, especially for the description of RCDs, SNOMED CT has the more granular dose form concepts, modelled modeled such that the more granular PDF concepts can be grouped under a less granular parent concept.

Basic dose form

In order to achieve the full definition of PDFs with this greater granularity, some additional basic dose forms have been created in SNOMED CT.  This occurs particularly for (but not exclusively) with oral dose forms:

• Hard and soft capsules:
  • Whilst the prescription process is rarely interested in the difference between hard capsules (two halves of a firm shell, one of which "slips over" the other to seal) and soft capsules (filled and sealed in a single process), it is of importance to the dispensing/administration process because of the there is a difference in divisibility and administration (open the capsule and sprinkle), and therefore the this granularity of description is needed to describe RCDs in national extensions. 
• Coated and film-coated concepts; moulded molded and compressed lozenges:
  • Although when describing abstract concepts such as clinical drugs, this level of granularity is not considered, it is frequently used in the description of RCDs since there are pharmacopoeial differences in the dose forms.   By having the greater granularity in the basic dose form attribute, RCDs can be fully described using the exactly matching PDF, and more abstract concepts can be grouped using the parent grouper basic dose form.

Powders and granules

For oral PDFs, powders and granules are differentiated, whereas, for parenteral products for human use, they are not, ; although EDQM does have a the term: "Granules for suspension for injection" it appears not to be used to describe any medicinal products.

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Administrable / Transform dose forms

As a general principle. if there is a pharmaceutical dose form that undergoes a transformation to another pharmaceutical dose form, the transformed PDF concept should be available in SNOMED CT International content even if there are no CDs that directly require it.  This is because even though the RCD would use the manufactured dose form, some extensions may also model "administrable clinical drugs" or equivalent concepts and require the administrable dose form.

For example, "Powder for intravesical solution" will transform to "Intravesical solution"; both must exist as PDF concepts.

Patterns for administration method

Wherever possible, patterns for administration method have been used for all PDF concepts, and these contribute to ensuring concepts have an exact semantic match,

Drops and sprays

Both drops and spray liquid dose forms are present in EDQM and in SNOMED CT.  In EDQM, there are some terms that use "drops" or "spray" as the basic dose form, and terms that use the more usual "solution/suspension/emulsion/dispersion" basic dose forms.   The former terms are original and are not recommended for use in new medicinal product authorisations. 

In SNOMED CT, there are also unspecified "drops" or "spray" concepts, where the basic dose form is not given (nor is a transformation, since there cannot be the certainty that a transform will not occur), and the definition is supported by the administration method (instil instill for drops and spray for sprays); these concepts are used to describe international clinical drugs.    SNOMED SNOMED CT also has the more granular concepts with the basic dose form and transformation specified , to support a direct match to the EDQM concepts, however, for these concepts, because of the lack of basic dose form; however, these concepts do not relate to each other directly in the hierarchy because of the lack of basic dose form.  

The administration method of "instilinstill" is also used for liquid instillationsinstallations, liquids administered to body cavities (bladder instillation, etc.).

"Rinse or wash" and

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bath

Several EDQM PDFs are described as "washes" (for example, "ear wash") where the semantic is of the liquid (containing one or more medicinal substance(s)substances) flowing over or through the site, flushing and cleansing it but not remaining in or at the site for a prolonged period.   To obtain semantically matching concepts, SNOMED CT has PDFs that have the administration method of "rinse/wash".   Irrigation solutions also use the administration method of "rinse/wash".

Other EDQM PDFs are described as for bathing, where the intended site is in contact with the liquid (containing one or more medicinal substance(s)) - often by immersion - for a prolonged period.

The device/physical object boundary

It can be challenging to find Finding the boundary between some dose forms and the products and medical devices, which are physical objects in SNOMED CT.   Medicinal , can be challenging. Medicinal products contain one or more substances that are intended "for treating or preventing disease, with the view to making a medical diagnosis or to restore, correct or modify physiological functions"* ¹, so in any situation where there is a requirement to "contain" those substances for administration, a pharmaceutical dose form should exist.   This means that, for example, PDFs for dialysis solutions are required , since these "contain" the substances that pull the toxins from the patient's blood into the dialysate. 

*  ¹ ISO 11615: Identification of Medicinal Products