Methotrexate

• Unruptured ectopic (hCG <5000, no FH, mass <3.5 cm)
• Persistent trophoblast post-salpingotomy
• Low-risk GTN

Inhibits dihydrofolate reductase → ↓ thymidine → halts trophoblast DNA synthesis.

• M — Mass <3.5 cm, no FH
• T — Tubal, unruptured, stable
• X — hCG <5000, no contraindication

Ectopic

50 mg/m² IM single dose; recheck hCG D4 & D7 (expect ≥15% fall)

Rheum (RA/psoriasis) — not in pregnancy

7.5–25 mg PO or SC once weekly + folic acid

• AbsoluteIntrauterine pregnancy / breastfeeding / renal-hepatic disease / immunodeficiency
• AbsoluteActive peptic ulcer or blood dyscrasia

• Abdominal pain D3–7 (separation pain)
• Stomatitis, ↑ LFTs
• Bone-marrow suppression

• • Highly teratogenic — contraception ×3 months after.
• • Avoid in breastfeeding.

• NSAIDs

  Avoid

  ↓ renal clearance → toxicity

• Trimethoprim

  Avoid

  Marrow suppression

• PPIs

  Caution

  ↑ MTX levels

• 💡 Avoid folic acid (antagonises) until hCG negative.
• 💡 Counsel: no alcohol, no sex (ovarian rupture risk), no sun.
• 💡 When used as a DMARD (RA/psoriasis), stop ≥3 months before planned conception in both women and men — one of only three DMARDs needing an active pre-conception washout (with leflunomide and mycophenolate).