Methotrexate has been used to treat moderate to severe psoriasis since the 1970s and belongs to the group of medicines known as 'systemics'. It is also used to treat psoriatic arthritis.
Methotrexate is for people with moderate to severe psoriasis who have not had a good response from, or are unsuitable for, topical treatments (treatments that are applied to the skin) or ultraviolet light therapy.
Methotrexate can also be prescribed for psoriatic arthritis. In this situation, it is known as a ‘Disease Modifying Anti-Rheumatic Drug’ (DMARD), meaning it acts on the actual condition itself, rather than just relieve the symptoms.
Methotrexate has a number of actions that account for its helpful effects in psoriasis and psoriatic arthritis. It slows down the production of new cells by the body’s immune system, and also reduces inflammation.
Methotrexate is usually taken in tablet form once a week. Sometimes it is taken as an injection, also once a week. A doctor will usually prescribe a very low dose at first, which will be gradually increased. Once the methotrexate is working well, the dose will be adjusted to the lowest level capable of maintaining the improvement that has been achieved.
People taking methotrexate will have regular blood tests - usually carried out by Dermatology Nurses, or by their own GP - to monitor possible effects of the treatment. These are required weekly at first, or when the dose is being altered, but once the dose of methotrexate is stable, monitoring tests are carried out every 2-3 months. People taking methotrexate should have an annual flu vaccination, but should check with a doctor or nurse before having any other vaccinations or taking other medication.
Methotrexate is often used on its own to treat psoriasis or psoriatic arthritis, however it is sometimes used in conjunction with other medications, in order to help the other medication work more effectively by preventing the body from building up antibodies.
There are lots of other medications that can interact with methotrexate, including over-the-counter products such as aspirin and ibuprofen, and certain vitamins or supplements. Anyone taking methotrexate should ensure that they tell their Dermatologist or Rheumatologist about all medications, over-the-counter products and supplements that they are taking, and should not take anything new without checking with their doctor or a Pharmacist first.
As with all medications, some side effects are possible when taking methotrexate. It is important to remember that not every person taking a medication will get all, or even any, of the possible side effects listed.
Because methotrexate works by reducing the activity of the immune system, it can make people taking it more prone to infections than they usually would be. If a serious infection occurs a doctor will most likely stop treatment with methotrexate. You should let your doctor know as soon as possible if you notice signs or symptoms of an infection, such as a raised temperature, fever or sore throat.
The immune system also protects against cancer, and it is thought that treatment with low doses of methotrexate may increase the risk of developing lymphomas (cancer that starts in the immune system). If this happens, treatment with methotrexate will be stopped. Sometimes, the lymphoma will resolve itself after methotrexate is stopped, whereas in other cases it will need to be treated.
The main risk of long-term methotrexate use is the potential for liver or kidney damage. In order to detect and treat this damage early, you will have regular blood tests and may be required to have occasional liver biopsies, where a thin needle is inserted through the skin to extract a small sample of liver tissue. In most people, treatment with methotrexate will be stopped, or the dose will be reduced, if signs of liver or kidney problems are found. If you develop jaundice (eyes or skin turning yellow), you should see a doctor as soon as possible.
The most common side effects of methotrexate are often managed by lowering the dose. Some of these common or dose-related side effects include feeling sick, tiredness, diarrhoea, mouth ulcers, rashes and hair loss.
If you have been prescribed methotrexate for treatment of your psoriasis, you may be asked to take part in the British Association of Dermatologists Biologics Interventions Register (BADBIR). This register is to compare the safety of different treatments for psoriasis and to see how well they work.
The information on this page is also available in our methotrexate information sheet.