FHIR R4 integration — ingest patient medication lists for richer drug safety checks

[sarvanithin]

Overview

Clinical systems expose patient data via FHIR R4 APIs (Epic, Cerner, etc.). If medguard can pull a patient's current medication list from a FHIR server, it can check the LLM query against the full medication profile — not just drugs mentioned in the message.

What to build

• medguard/integrations/fhir.py — FHIRMedicationLoader
  • get_medications(patient_id, fhir_base_url, token) → list[str] drug names
  • Parses MedicationRequest and MedicationStatement FHIR resources
  • Uses httpx (already a dependency)
• MedGuard.achat(message, fhir_context=None) — optional FHIR context
• When fhir_context provided, drug safety checks include FHIR medications + message drugs

FHIR endpoint example

GET {base}/MedicationRequest?patient={id}&status=active
Authorization: Bearer {token}

Files to create/modify

• medguard/integrations/fhir.py — new file
• medguard/core.py — accept optional fhir_context in achat
• medguard/guardrails/drug_safety.py — merge FHIR drugs with extracted drugs

Acceptance criteria

• FHIRMedicationLoader.get_medications(...) parses FHIR MedicationRequest JSON
• Medications from FHIR are included in drug safety check
• Works with public FHIR test server (https://hapi.fhir.org/baseR4)
• Tests use mocked FHIR responses

Resources

• FHIR R4 spec: https://hl7.org/fhir/R4/
• Public test server: https://hapi.fhir.org/baseR4