Add RxNorm drug normalization via UMLS #59
Description
Summary
Use RxNorm vocabulary from UMLS for brand-to-generic drug mapping, dosage form normalization, and ingredient extraction.
Details
- Clinical text often uses brand names (Keytruda) vs generic (Pembrolizumab) interchangeably
- RxNorm provides canonical drug concept hierarchy: ingredient -> clinical drug -> branded drug
- Improves entity extraction accuracy for varied drug name mentions
- Enables dosage form awareness (tablet vs injection vs topical)
Acceptance Criteria
- Parse RXNCONSO and RXNREL from UMLS RxNorm subset
- Build brand-to-generic mapping table
- Integrate normalization into entity extraction pipeline
- Test with drug name variants in evaluation cases
Priority: P3