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Chemotherapy / Immunosuppressant — Head and Neck / Granulomatosis

Methotrexate

Brand names: Methofar, Zlatal, Methofar

Methotrexate is taken WEEKLY (not daily) as a disease-modifying drug in rheumatoid and other inflammatory arthritis, psoriasis and Crohn's disease; much higher doses are used in some cancers.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It inhibits dihydrofolate reductase and other folate-dependent enzymes, reducing cell proliferation and modulating inflammation.

Prescribing in practice

  • For non-cancer use it is taken ONCE A WEEK — accidental daily dosing causes fatal toxicity (a recognised never-event); folic acid is co-prescribed on a different day to reduce side effects.
  • It causes myelosuppression, hepatotoxicity and pneumonitis, and is teratogenic (effective contraception; stop before conception).
  • It interacts dangerously with trimethoprim/co-trimoxazole (additive antifolate — avoid) and with NSAIDs in renal impairment.

Monitoring

Monitor FBC, liver function and renal function regularly (closely at first); review for cough or breathlessness (pneumonitis).

Counselling the patient

  • Take it ONCE A WEEK on the same chosen day — never daily.
  • Take your folic acid as directed, on a different day.
  • Report sore throat/fever/bruising, breathlessness or a dry cough; use effective contraception; avoid trimethoprim-containing antibiotics.

Evidence & guidelines

A first-line DMARD for rheumatoid arthritis (NICE NG100), with strict weekly dosing and blood monitoring.

Reference: MHRA Methotrexate guidance; BSR GPA Guidelines 2014; NICE NG100; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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