Add the following guidance under the Use cases and overview page under the Additional Guidance section (as the first section). Specific Drug Coverage Details RxNorm codes and descriptions were chosen as the mechanism for searching and describing covered drugs for consumer use because that is what consumers will generally have access to given the requirements laid out in US regulation. RxNorm is also the code system used for many outpatient pharmacy prescribing transactions. RxNorm provides a consumer accessible categorization for prescribable drugs. This categorization may not be specific enough for payers that have very detailed coverage constraints they feel are necessary to express to their members. This IG Provides the following ways to express various levels of coverage (coverage status, requirements, or costs) for multiple drugs represented under one RxNorm code. Specific drugs identified by unique  FormularyDrug  resource instances that are  associated to a Formulary with specific coverage conditions, requirements, and costs through a  FormularyItem . A specific drug code using NDC or other code system is included as a  FormularyDrug  MedicationKnowledge.code.coding that includes the specific name in the display to enable searching. Drugs identified by a general RxNorm code in a single  FormularyDrug  MedicationKnowledge resource with specific coverage conditions and requirements communicated in the referenced  FormularyItem. Specific details including drugs covered or not covered, coverage conditions, or requirements are specified in the  FormularyItem  Basic.extensions [usdf-AdditionalCoverageInformation-extension] .   To the Searching Formulary Drugs section, at the bottom of the main section add: Note: In addition to the guidance and requirements below regarding searching for drugs based on an RxNorm code or display, servers may wish to support additional coding systems and display values in order to represent specific drugs that may have the same RxNorm code, but have different coverage specifics as defined in [Specific DrugCoverage Details] (specific-drug-coverage-details). This may result in more than one [FormularyDrug] ( StructureDefinition-usdf-FormularyDrug.html) with the same RxNorm code and display value.