A disease-modifying antirheumatic drug (DMARD)
Methotrexate
A cornerstone treatment for rheumatoid arthritis and severe psoriasis that calms an overactive immune system — taken once a WEEK, never daily, with folic acid and regular blood tests.
What is Methotrexate?
Methotrexate is a disease-modifying medicine used at low doses for rheumatoid arthritis, psoriatic arthritis and severe psoriasis. It dampens the overactive immune response that drives these conditions. The single most important safety point is that it is taken once a WEEK, not daily — daily dosing by mistake can be fatal. Folic acid on a different day reduces side effects, and regular blood tests monitor the blood count and liver.
Education and reference only. This is a plain-language guide to Methotrexate — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Methotrexate is one of the most important long-term ("disease-modifying") treatments for inflammatory conditions such as rheumatoid arthritis and psoriatic arthritis, and for severe psoriasis. At the low doses used for these conditions it works as an immune-calming and anti-inflammatory medicine, slowing the disease and protecting the joints or skin rather than just easing symptoms. (Much higher doses are used in cancer care — a completely different setting.) It is usually a long-term treatment, started and supervised by a specialist, and taken as a weekly tablet or injection.
How it works
Methotrexate interferes with the way rapidly dividing cells use folate (a B vitamin), and it boosts the release of a natural anti-inflammatory chemical called adenosine. At the low weekly doses used in arthritis and psoriasis, the overall effect is to calm the overactive immune activity that drives joint or skin inflammation, reducing damage over time. Because it affects folate handling, a separate folic acid supplement is given on a different day to reduce side effects without blocking the treatment's benefit.
What it treats
Conditions Methotrexate is used for
Practical use
How to take Methotrexate
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it ONCE A WEEK on the same day each week — never daily. Keep a clear record; accidental daily dosing is dangerous.
- Take your folic acid on a different day from the methotrexate (for example, methotrexate on a Monday, folic acid later in the week), as advised.
- Attend all monitoring blood tests — these are essential for safe long-term use.
- Avoid alcohol excess (it adds to the strain on the liver), and do not take over-the-counter or new medicines without checking, especially anti-inflammatory painkillers and the antibiotic trimethoprim.
- Use reliable contraception, and tell your team before any planned pregnancy — it must be stopped well beforehand for both partners.
Weighing it up
Advantages & disadvantages of Methotrexate
Advantages
- A well-proven, first-choice DMARD that can slow disease and protect joints, not just relieve symptoms.
- Taken only once a week, and low cost.
- Works well alone or as the backbone alongside biologic or targeted treatments.
Disadvantages
- Requires strict weekly (not daily) dosing and regular blood-test monitoring.
- Can affect the liver, blood count and, rarely, the lungs; raises infection risk.
- Must not be used in pregnancy and needs reliable contraception for both partners.
Practical use
Good to know
The defining safety rule with methotrexate is that it is taken ONCE A WEEK — always on the same, chosen day — and never every day. Accidental daily dosing is dangerous and can be fatal, so your prescription, packaging and record clearly state the weekly day. You will also take folic acid on a different day of the week, which reduces mouth ulcers, nausea and other side effects. Regular blood tests check the blood count, liver and kidneys. Report a sore throat, fever, unusual bruising or bleeding, or new breathlessness or a dry cough promptly. Both men and women must avoid conception during treatment and for a period afterwards, as it can harm a developing baby.
Who should not take it / use with caution
- Women who are pregnant or breastfeeding, and anyone (male or female) trying to conceive — it can harm a developing baby and must be stopped beforehand.
- People with significant liver disease, heavy alcohol use, significant kidney impairment, or certain blood or active infection problems.
- People with significant existing lung disease, used only with caution and specialist judgement.
Monitoring
- Full blood count (for bone-marrow effects)
- Liver function tests
- Kidney function; and lung symptoms (new cough or breathlessness)
Side effects
- Common: nausea, mouth ulcers, tiredness and, sometimes, hair thinning — often eased by folic acid and by taking it as an injection.
- Important: effects on the liver and blood count (picked up on monitoring blood tests) and an increased risk of infection — report fever, sore throat, or unusual bruising or bleeding.
- Rare but serious: inflammation of the lungs — report a new dry cough or breathlessness promptly.
Key interactions
- The antibiotic trimethoprim (and co-trimoxazole) must generally be avoided — together they can seriously suppress the bone marrow.
- Anti-inflammatory painkillers (NSAIDs such as ibuprofen and naproxen) and some other drugs can raise methotrexate levels; this is managed with care and monitoring.
- Live vaccines are generally avoided while on it; alcohol adds to the risk of liver harm.
Available as: Weekly tablets, or a weekly pre-filled injection (which can cause less nausea); a liquid form is also available.
Answers
Methotrexate: frequently asked questions
Why is it so important that methotrexate is taken weekly?
At the doses used for arthritis and psoriasis, methotrexate is designed to be taken once a week. Taking it every day by mistake causes a dangerous overdose that can be fatal. Always take it on your chosen day only, keep a clear record, and never try to "catch up" a missed dose by taking extra.
Why do I take folic acid with methotrexate?
Folic acid, taken on a different day, reduces common side effects such as mouth ulcers, nausea and tiredness, without stopping methotrexate from working. It is a standard part of treatment — take it as your team advises, usually not on the same day as the methotrexate.
Can I drink alcohol on methotrexate?
Both methotrexate and alcohol can affect the liver, so heavy drinking is avoided. Many teams accept modest, occasional alcohol within national low-risk limits, but this should be agreed with your prescriber and balanced against your blood-test results.
Can I take methotrexate if I want to have a baby?
No — methotrexate can harm a developing baby and must be stopped well before conception, for both men and women, with reliable contraception used during treatment. Discuss family planning with your specialist team in advance so treatment can be switched safely.
What should I report straight away?
Contact your team promptly if you develop a fever or sore throat, unusual bruising or bleeding, mouth ulcers that are severe, or a new dry cough or breathlessness — these can signal effects on the blood count, an infection, or (rarely) the lungs.
Authoritative sources
- BNF: Methotrexate.
- electronic Medicines Compendium (SmPC): Methotrexate.
- NICE NG100: Rheumatoid arthritis in adults; MHRA methotrexate weekly-dosing safety guidance.
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