I have significant psoriasis and my skin specialist has suggested starting treatment with methotrexate and folic acid. I had always been treated with creams and did not know this treatment existed, including as an injection. What is methotrexate and how does it work?

Hello Isabel,

That is an excellent question and, in fact, a very common concern when we propose this treatment for the first time.

Psoriasis is not solely a skin disease. It is actually a chronic inflammatory disease of immune origin, in which the immune system sends signals that make skin cells multiply much faster than normal. As a result, red plaques, scaling, itching and, in some patients, pain or joint involvement appear.

When psoriasis is mild, local treatments such as creams or ointments are usually enough. However, when the disease is more extensive, significantly affects quality of life or topical treatments are no longer sufficient, we need to act from within the body.

This is where methotrexate comes in.

Methotrexate is a medication we have been using for decades and whose action we understand very well. At the doses used in psoriasis, it works by regulating the immune system's response and reducing inflammation, which helps to curb the excess activity responsible for the lesions. In other words, it does not only treat the visible plaques, but acts on the mechanism that produces them.

It can be given as tablets or as a subcutaneous injection once a week. In many patients I prefer the subcutaneous route because it offers more stable absorption and often causes fewer digestive complaints.

It is important to remember that methotrexate is taken only once a week, never every day. This is one of the most important aspects of the treatment.

Along with methotrexate we usually prescribe folic acid (Acfol®). This is not because you have a vitamin deficiency, but because it helps reduce some possible side effects of the treatment, such as digestive discomfort, mouth ulcers or certain laboratory abnormalities. It should be taken on the day indicated by your doctor, normally on a different day from the methotrexate.

Like any systemic treatment, it requires regular monitoring. Before starting it and during treatment we carry out blood tests to check the function of the liver, the kidneys and the blood cells. Thanks to this monitoring, the treatment is usually very safe when it is well indicated and properly controlled.

There are also nowadays the so-called biologic medicines, which are very effective for certain patients. However, methotrexate remains one of the reference treatments in moderate to severe psoriasis because of its efficacy, its extensive track record and its excellent benefit-to-risk ratio in many patients.

My advice is not to be afraid of the name of the medication. The methotrexate used in skin medicine is given at doses far lower than those used in oncology and with a completely different aim: to control inflammation and improve quality of life.

When the treatment is well indicated and the patient carries out the recommended check-ups, the results are usually very satisfactory and many people manage to keep their psoriasis under control for years.

I hope I have answered your question.

Warm regards,

Doctor Florian A. Vallecillo Cabrera