Methotrexate
Indications
Methotrexate is used at low doses, once a week, for rheumatoid arthritis, severe psoriasis, psoriatic arthritis and some other inflammatory conditions. At higher doses it is used by cancer specialists to treat certain cancers, such as some leukaemias, lymphomas, breast cancer and choriocarcinoma. It is also used in hospital for some ectopic pregnancies.
How It Works
It blocks an enzyme that cells need to use folic acid to make DNA. At low weekly doses it calms the overactive immune system that causes joint and skin inflammation; at high doses it stops fast-growing cancer cells from dividing.
Dosage and Administration
- Arthritis and psoriasis: taken ONCE A WEEK, on the same day each week, at the dose prescribed. Never take it every day; daily dosing by mistake has caused deaths.
- Your doctor will usually also prescribe Folic Acid to take on a different day of the week to reduce side effects.
- Cancer and ectopic pregnancy: doses and schedules are set by the specialist, as prescribed. Injections are given by a doctor or nurse.
- Children: only as prescribed.
Interactions
- Trimethoprim and Co-trimoxazole can cause dangerous bone marrow suppression with methotrexate and should be avoided.
- NSAIDs such as Ibuprofen and Diclofenac, Penicillins, Probenecid and high-dose proton pump inhibitors such as Omeprazole can raise methotrexate levels.
- Alcohol and other medicines that can harm the liver (for example Leflunomide) increase the risk of liver damage.
- Live vaccines should be avoided during treatment.
Contraindications
- Pregnancy, or planning pregnancy (in women or men) without reliable contraception.
- Breastfeeding.
- Severe kidney or liver disease, or heavy alcohol use.
- Existing blood disorders such as low white cells, platelets or severe anaemia.
- Serious active infections, including tuberculosis, or weakened immunity.
Side Effects
Common: nausea, loss of appetite, mouth ulcers, tiredness, headache, mild hair thinning and upset stomach, often for a day or two after the weekly dose.
Get urgent medical help if you have a sore throat, fever, chills or other signs of infection, unusual bruising or bleeding, a new dry cough or breathlessness, severe or many mouth ulcers, severe diarrhoea or vomiting, yellow skin or eyes or dark urine, or a blistering or peeling rash. Also seek help at once if you have taken it more often than once a week by mistake.
Pregnancy and Lactation
It can cause miscarriage and serious birth defects. Both women and men must use reliable contraception during treatment and for some months after stopping (often 3 to 6 months; follow your doctor's advice). Do not breastfeed while taking it.
Precautions and Warnings
Regular blood tests (blood count, liver and kidney tests) are essential. Keep alcohol to a minimum or avoid it. Tell any doctor or dentist that you take methotrexate. Avoid contact with people who have chickenpox or shingles and report exposure. Wash your hands after handling the tablets; pregnant women should not handle broken tablets.
Overdose
Overdose, including taking it daily instead of weekly, is dangerous and can cause severe mouth ulcers, bleeding, infection and organ damage. Get emergency medical help straight away; hospitals have a specific antidote (folinic acid), which works best when given early.
Therapeutic Class
Antimetabolite (folic acid antagonist); disease-modifying antirheumatic drug (DMARD) and anticancer medicine.
Storage
Store below 30°C in a dry place, away from light and out of the reach of children.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.
All brands of Methotrexate