About methotrexate
Antimetabolite immunosuppressant and antineoplastic
Used for
- Rheumatoid arthritis and juvenile idiopathic arthritis
- Severe psoriasis
- Certain cancers
Usual adult dose
For rheumatoid arthritis or psoriasis, usually 7.5–25 mg once weekly; cancer doses vary by regimen.
Usual dose in children
For juvenile arthritis, commonly 10–15 mg/m² once weekly; specialist-directed doses vary.
Common side effects
- Nausea, vomiting, or mouth sores
- Low blood counts and increased infection risk
- Liver injury
- Lung inflammation
Important warnings
- Take only once weekly for inflammatory conditions; daily dosing errors can be fatal.
- Can cause severe liver, lung, kidney, blood, or immune-system problems.
- Avoid alcohol; monitoring with blood tests is essential.
- Seek urgent care for serious infection, unusual bleeding, severe breathlessness, or pregnancy exposure.
Pregnancy
Can cause miscarriage and birth defects; contraindicated for non-cancer use during pregnancy. Cancer treatment requires specialist assessment.
Breastfeeding
Generally not recommended; small amounts may enter milk. Specialist guidance is needed, especially with high-dose treatment.
Interactions
- Trimethoprim or co-trimoxazole can increase blood toxicity.
- NSAIDs and some antibiotics may raise methotrexate levels or toxicity.
- Live vaccines may cause infection; avoid during treatment.
- Alcohol and other liver-toxic medicines increase liver injury risk.
AI-generated from general medical knowledge, not from this product's official leaflet. It may be incomplete or out of date. Not medical advice — ask a pharmacist or doctor before making any decision.