What is methotrexate?
Methotrexate is an immunosuppressant medication that has been licensed for many years to treat a number of inflammatory conditions, including psoriasis and rheumatoid arthritis. It is now being used with increasing frequency for severe eczema. It is available as tablets or can be injected.
How does methotrexate work?
Methotrexate prevents cells of the immune system from dividing. It is not entirely clear how it reduces the severity of eczema, but we do know that it blocks several important enzymes that are found inside cells and affects those that are actively growing (e.g. the skin).
It takes several weeks for methotrexate to accumulate inside cells. Therefore, once you start taking methotrexate, it can take several weeks before you notice any improvement in your skin. Methotrexate cannot cure your eczema but it should significantly improve the severity of your condition and can be taken for many years.
When is methotrexate used?
Methotrexate is used off-licence for adults and children with severe eczema who are troubled with repeated, widespread flare-ups of the disease, or who have eczema that is hard to control with topical treatments alone.
Methotrexate is taken in tablet or injection form, once a week, on the same day each week. It must NEVER be taken more than once a week. Methotrexate is usually started at a low dose, such as 5 mg. If there are no side effects, the dose is increased weekly to a regular dose of 15–20 mg.
Who should NOT take methotrexate?
People who have low blood counts (anaemia, leukopenia, thrombocytopenia) or abnormal kidney or liver function should not take methotrexate.
Methotrexate can cause birth defects, miscarriage and stillbirth, so should not be taken during pregnancy. Both men and women should stop taking methotrexate at least 6 months before attempting to conceive. Women should not breastfeed since the drug can be excreted in breast milk.
Caution is needed in people who are obese or who have mild liver or kidney disease, infections or diabetes. The risk of liver damage from methotrexate is increased by alcohol, therefore if you are taking methotrexate you should stick within the recommended limits or, better still, avoid alcohol altogether.
What are the side effects of methotrexate?
It is important to remember that most people do not experience side effects that prevent them from taking methotrexate. Any side effects that do occur are usually minor and will improve with time.
The most common side effect is nausea, which usually occurs on the day methotrexate is taken. Your doctor can advise you on how to minimise this, but regular folic acid, anti-sickness tablets and changing from methotrexate tablets to injections can help.
Abnormalities in liver function and full blood counts can occur, especially during the first few weeks of methotrexate treatment. For this reason, people taking methotrexate have regular blood tests, which are more frequent at the start of treatment. The risk of liver damage from methotrexate is increased by alcohol. Therefore, if you are taking methotrexate, it is best to avoid alcohol altogether.
Less commonly (<5%), people develop mouth ulcers, rashes, diarrhoea and significant abnormalities in blood counts.
Because methotrexate is an immunosuppressant medication, people taking it can also be more susceptible to some infections. For people with eczema, this can include viral infections in the skin, such as herpes simplex. However, most people notice fewer infections of their eczema while on methotrexate, as their eczema is better controlled. You should have an annual flu jab and also inform your doctor or specialist dermatology nurse if you experience a fever, sore throat, any infection (including a change in your eczema) or unexplained bleeding/bruising.
Gradual hair-thinning can also affect some people, but hair usually grows back when the person stops taking methotrexate.
One effect of methotrexate is to reduce the folic acid in your body. Folic acid is a vitamin, and supplementing it reduces some of the side effects of methotrexate (e.g. nausea). For this reason, people on methotrexate are given folic acid tablets.
For more information on methotrexate, please see our Methotrexate factsheet