Normalize and verify drug names against RxNorm, the canonical US drug vocabulary from the NIH. Two modes: term ("tylenol 500mg", brand or generic, typos tolerated) returns ranked RxCUI candidates with normalized names and match scores; rxcui returns the canonical concept (name, term type like IN=ingredient / SBD=branded drug / SCD=clinical drug, suppression flag) plus related concepts — active ingredients, brand names, and available dose forms. Use before writing prescriptions data, drug interactions queries, or pharmacy integrations: verify the drug exists and get its stable identifier instead of trusting model memory. Sibling: /api/medical/icd10 (diagnosis codes). Public-domain NIH data.