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The terms for drug interventions come from the following vocabularies:

• RxNorm 
• WHO ATC
• SNOMED CT

Drug categories

WHO ATC and SNOMED CT are used for drug categories. 

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Both RxNorm and WHO/ATC have terms to cover cases in which two or more individual drugs are combined into a single formulation (pill, solution, inhaler etc.) so that they can be easily administered together.  It is better to ignore these combination terms and annotate the individual drug components using AND. 

Non-drug interventions

Terms for all non-drug interventions are drawn from SNOMED CT.  As with P, only selected subsets of this vocabulary are included in the Cochrane vocabulary.

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