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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.

US labelling (FDA)

Reference — US labelling, may differ from UK

• Instruct patients and caregivers to take the recommended dosage as directed, because medication errors have led to deaths. (2.1, 5.9) • Verify pregnancy status in females of reproductive potential before starting methotrexate tablets. (4, 5.1) • ALL: The recommended dosage is 20 mg/m 2 orally once weekly as a part of a combination chemotherapy maintenance regimen. (2.2) • Mycosis fungoides: The recommended dosage is 25 to 75 mg orally once weekly as monotherapy; 10 mg/m 2 orally twice weekly as part of combination chemotherapy. (2.2) • Relapsed or refractory non-Hodgkin lymphoma: The recommended dosage is 2.5 mg orally two to four times per week as part of metronomic combination …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2024-06-04. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

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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