DaVinci Payer Data Exchange (PDex) US Drug Formulary
2.0.1 - STU 2 United States of America flag

DaVinci Payer Data Exchange (PDex) US Drug Formulary, published by HL7 International / Pharmacy. This guide is not an authorized publication; it is the continuous build for version 2.0.1 built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/davinci-pdex-formulary/ and changes regularly. See the Directory of published versions


Official URL: http://hl7.org/fhir/us/davinci-drug-formulary/ImplementationGuide/hl7.fhir.us.davinci-drug-formulary Version: 2.0.1
IG Standards status: Trial-use Computable Name: Formulary
Page standards status: Informative

DaVinci Payer Data Exchange (PDex) US Drug Formulary

This implementation guide defines a FHIR interface to a health insurer's drug formulary information for patients/consumers. A drug formulary is a list of brand-name and generic prescription drugs a health insurer agrees to pay for, at least partially, as part of health insurance coverage. Drug formularies are developed based on the efficacy, safety, and cost of drugs. The primary use cases for this FHIR interface enable consumers/members/patients to understand the costs and alternatives for drugs that have been prescribed, and to compare their drug costs across different insurance plans.

A key architectural issue that is beyond the scope of this implementation guide is how a user finds the FHIR endpoint for a particular formulary. This implementation guide assumes that the FHIR endpoint is known to the user.


This Implementation Guide (IG) includes a number of profiles, extensions, search parameters, and value sets.

  • PayerInsurancePlan: The PayerInsurancePlan profile of the FHIR R4 InsurancePlan resource defines the health insurance product including coverage benefits that are offered and additional information about the offering, such as a coverage area, contact information, brochure locations, etc. The health insurance product can offer one or more types of coverage, each of which may define a plan of covered benefits with the particular cost sharing structure offered to a consumer. Health insurance plans that include drug coverage reference a formulary that provides details about drugs that are covered under the plan including requirements and limitations of the coverage specific to each drug.
  • Formulary: The Formulary profile of the FHIR R4 InsurancePlan resource provides general information about a formulary and acts as an organizing construct that associated FormularyItem resources point to. The Formulary combined with its associated FormularyItem and FormularyDrug resources represent a formulary list that includes the set of drugs covered and the requirements and limitations of that coverage.
  • FormularyItem: The FormularyItem profile of the FHIR R4 Basic resource describes a drug's relationship to a formulary, including drug tier, prior authorization requirements, and more.
  • FormularyDrug: The FormularyDrug profile of the FHIR R4 MedicationKnowledge resource provides information about a prescribable drug including its RxNorm code and dose form. Drugs not included in a formulary may not be represented by a FormularyDrug instance.

A detailed description of the relationship between the profiles in this guide can be found in the Formulary Structure section.

Several searchParameters have been defined in this guide to facilitate the anticipated use cases. See the Anticipated Client Queries section for a description of how to query for resources in support of the anticipated use cases. Below are some of the search parameters defined in this guide.

  • coverage-type: Makes the coverage.type CodeableConcept of each PayerInsurancePlan accessible for query to find InsurancePlan resources that have a specific coverage type, like drug coverage.
  • formulary-coverage: Makes the coverage extension formulary reference of each PayerInsurancePlan accessible for query to find InsurancePlan resources that reference specific formulary.
  • coverage-area: Makes the coverageArea reference of each PayerInsurancePlan accessible for query to find an InsurancePlan by coverage location.
  • formulary: Makes the extension Formulary reference of each FormularyItem accessible for query to find drugs included in a particular formulary.
  • drug-tier: Makes the extension DrugTier codeableConcept of each FormularyItem accessible for query to find drugs in a specific tier.
  • pharmacy-benefit-type: Makes the extension PharmacyBenefitType codeableConcept of each FormularyItem accessible for query to find drugs in available through a specific pharmacy benefit type.
  • drug-name: Makes the RxNorm name of eachFormularyDrug accessible for query to find drugs by name, strength and form.

Information about searching for formulary drugs can be found in the Searching for Formulary Drugs section.

Expected Users

This Implementation Guide is intended for insurers within the United States. Currently, many insurers make their formularies available to patients using PDFs or drug search forms through their websites. Providing formularies using FHIR may allow patients to find alternatives to reduce their medication costs, easily comparison-shop between plans, and could help insurers educate consumers about the differences between various drug tiers and pharmacy benefit types.

Disclaimers and Assumptions

  • Drug Formulary Data Use: The intent of this implementation guide is to make the plan-level information regarding formulary content and cost-sharing available through a standard interface to enable consumers to have an informed discussion with their practitioner about their medication options. Most consumers will access this data through a third party application. These applications SHOULD clearly communicate to the user that the cost-sharing information in the formulary may not tell them precisely what they will pay at the pharmacy, and might not fully reflect their drug benefit. Situational inclusions, exclusions, and requirements may apply. The presence or lack of presence of a particular drug in a query response should not be construed as a guarantee of coverage or lack thereof. An insurer may only support searching for drugs that are part of the formulary or formularies in the context of the query. Insurers SHOULD provide appropriate information and disclaimers regarding the interpretation and expected use of the data made available through this guide, including how the presence or lack of presence of a drug should be interpreted.
  • The FHIR MedicationKnowledge Resource is immature: The HL7 Pharmacy WG felt that MedicationKnowledge was the best choice for representing a formulary drug, even with its low maturity, since it is more suitable as an artifact and already included some of fields that would be required as extensions to the Medication resource. The MedicationKnowledge resource and FormularyDrug profile will co-evolve moving forward.
  • The formulary endpoint is known to the client: This guide assumes that the formulary endpoint is known to the client. The mechanism for FHIR endpoint discovery is important, but considered out of scope for this guide.