Methotrexate
Antimetabolite / DMARD- Drug Class
- Antimetabolite / DMARD
- Mechanism of Action (MOA)
- Inhibits dihydrofolate reductase → ↓ purine/pyrimidine synthesis (antiproliferative and immunomodulatory).
- Black Box Warning
- Embryo-fetal toxicity (contraindicated in pregnancy for non-cancer use), severe hypersensitivity/anaphylaxis, serious reactions of bone marrow, GI tract, liver, lungs, skin and kidneys, and fatal medication errors from daily instead of WEEKLY dosing.
- Clinical Notes
- RA, psoriasis, ectopic pregnancy (off-label), chemotherapy. Dose WEEKLY (not daily) for RA; supplement folic acid; leucovorin rescue with high-dose therapy. Avoid in pregnancy.
- Source
- FDA label
Sources
Reviewed September 2026- FDA label — FDA / DailyMed
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