Rheumatology
Methotrexate
A disease-modifying antirheumatic drug (DMARD) — A weekly immune-modifying drug for rheumatoid arthritis, psoriasis and more — safe when the rules are followed.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
What it is
Methotrexate is a long-term immune-modifying treatment used in rheumatoid and other inflammatory arthritis, psoriasis, inflammatory bowel disease and some other conditions. (Much higher doses are used separately in cancer care.)
How it works
At the low weekly doses used here it dampens the overactive immune and inflammatory processes that drive these diseases, slowing joint damage and calming skin or bowel inflammation rather than just easing symptoms.
In practice
In practice the single most important safety rule is that methotrexate for these conditions is a ONCE-WEEKLY medicine — accidental daily dosing has caused fatal toxicity, so the day of the week is fixed and clearly communicated. Folic acid is co-prescribed (on a different day) to reduce side-effects, regular blood tests track the liver and bone marrow, and patients are told to report breathlessness, cough, mouth ulcers or signs of infection. It interacts with several drugs (including trimethoprim and high-dose NSAIDs) and must be stopped well before conception by either partner.
Examples
Practical use
How to take it & use it well
- For conditions like rheumatoid arthritis and psoriasis, methotrexate is taken ONCE A WEEK, not daily; taking it every day by mistake can be fatal, so be absolutely certain of your weekly schedule.
- Choose a fixed day of the week and stick to it, and keep a clear record so there is no confusion about when your dose is due.
- Take your prescribed folic acid on a different day from your methotrexate to help reduce side effects such as mouth ulcers and nausea.
- Attend all blood test appointments, as your clinician monitors your blood count, liver and kidneys throughout treatment.
- Avoid alcohol or keep it well within low limits, as both alcohol and methotrexate can affect the liver.
- Report promptly any sore throat, fever, unusual bruising, breathlessness or a new dry cough, as these can signal serious side effects.
Common uses
- Rheumatoid and other inflammatory arthritis
- Moderate-to-severe psoriasis
- Some inflammatory bowel and autoimmune conditions
Monitoring
- Full blood count, liver and renal function on a regular schedule
- Breathlessness or cough (rare lung effects)
- Pregnancy planning and interacting medicines
Weighing it up
Advantages & disadvantages
Advantages
- It is an effective long-term treatment for rheumatoid arthritis, psoriasis and other inflammatory conditions.
- It can slow joint damage in inflammatory arthritis, protecting function over time.
- Once-weekly dosing is convenient when taken correctly.
- It is often a cornerstone treatment that other medicines can be added to if needed.
Disadvantages
- Weekly dosing is easy to confuse with daily medicines, and accidental daily use can be fatal.
- It can suppress the bone marrow and affect the liver and lungs, so regular blood tests are essential.
- Nausea, tiredness, mouth ulcers and hair thinning can occur.
- It must be avoided in pregnancy and around conception, as it can seriously harm a developing baby.
Key safety principles
What to watch for
- ONCE-WEEKLY dosing — daily dosing by mistake can be fatal; the day must be clear.
- Liver toxicity and bone-marrow suppression — regular blood monitoring is essential.
- Teratogenic — effective contraception for both partners; many interactions (e.g. trimethoprim, high-dose NSAIDs).
Key interactions
What to avoid or check alongside
- Trimethoprim and co-trimoxazole can dangerously add to methotrexate's effect on the bone marrow and must be avoided.
- Anti-inflammatory painkillers (NSAIDs) and aspirin can raise methotrexate levels, increasing toxicity, especially at higher methotrexate doses.
- Some antibiotics, such as penicillins, can reduce how methotrexate is cleared and raise its levels.
- Other medicines that affect the bone marrow or liver add to the risk of toxicity.
- Live vaccines are generally avoided because methotrexate weakens the immune response.
Patient & carer advice
- Take it on the SAME day each week — never daily
- Take your folic acid as directed (on a different day)
- Report a sore throat, fever, mouth ulcers, breathlessness or new cough
Use with
Related clinical calculators
Dose and risk decisions for this class often depend on renal function, weight or bleeding/stroke risk. These tools help:
Answers
Methotrexate: frequently asked questions
Why is it so important that methotrexate is taken weekly?
For arthritis and skin conditions, methotrexate is a once-weekly medicine. Taking it every day by accident can cause severe, even fatal, toxicity. Always confirm your weekly day, keep the tablets clearly labelled, and double-check before each dose.
Why do I take folic acid with methotrexate?
Folic acid helps reduce common side effects of methotrexate such as nausea, mouth ulcers and tiredness. It is taken on a different day from your methotrexate dose so it does not reduce the medicine's intended effect.
Can I drink alcohol on methotrexate?
Both alcohol and methotrexate can affect the liver, so it is best to avoid alcohol or keep well within low limits and follow your clinician's advice. Regular blood tests help monitor your liver during treatment.
Can I take methotrexate if I might become pregnant?
No. Methotrexate can seriously harm a developing baby and must be avoided in pregnancy and around conception. Effective contraception is needed during treatment, and you should plan any pregnancy carefully with your specialist well in advance.
What symptoms should make me seek urgent advice?
Contact your clinician promptly if you develop a sore throat, fever, mouth ulcers, unusual bruising or bleeding, a new dry cough or breathlessness, as these can signal serious effects on blood cells, the liver or the lungs.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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