In the Formulary 1.1.0 IG, the search parameters for Formulary Drug (DrugName, DrugTier, and DrugPlan) include the comparator ("eq") in their structure definitions, but the search types are "string" and "token".

In the Formulary 1.2.0 IG, the issue persists for the search parameter drug-name.

The comparator should be removed.

Including a comparator for a string or a token while using the syntax described for number, date or quantity creates ambiguity in the search string (e.g., DrugName=eqPaxil vs. DrugName=Equagesic) and the logic for implementing the search type.

A change request for FHIR R4 was opened in parallel to prevent this from occurring in the future by placing a constraint on comparator by search type. https://jira.hl7.org/browse/FHIR-37622.

This issue was discussed on Zulip: https://chat.fhir.org/#narrow/stream/197730-Da-Vinci-PDex-Drug-Formulary/topic/syntax.20for.20comparator.20eq.20in.20token.20or.20string