Methotrexate and Psoriasis: What Should You Know?

Before beginning the treatment, the doctor must ensure that there are no contraindications. A blood test is performed to assess the functioning of the kidneys, liver, blood cells, and to screen for potential infections. For women of childbearing age, a pregnancy test is conducted. A chest X-ray is performed in certain cases.

If the results are normal, the treatment is prescribed in the form of tablets or subcutaneous injections, to be taken or administered once a week. The dose of methotrexate typically ranges from 7.5 to 25 mg per week, with an average of 15 mg per week. The tablets can be taken all at once or divided between morning and evening, on the specified day of the week for the treatment. They are swallowed during meals.

In order to monitor your tolerance to the treatment, blood tests are conducted after 7 days, then every 15 days during the first month, followed by once a month every 2 to 3 months. If necessary, your doctor can adjust the dose of methotrexate by increasing or decreasing it. In some cases, treatment monitoring may include regular examinations.

In the case of psoriasis, a chronic disease, the duration of treatment with methotrexate can range from several months to several years, as long as it is tolerated and effective. This is a suspension treatment that does not cure the disease but allows for control of its progression throughout the duration of the treatment.

The results of the treatment vary from person to person, but in approximately 70% of cases, an improvement in psoriasis is observed. Some individuals may notice an improvement as early as the first month of treatment, but the maximum effect is typically achieved after about 3 to 4 months of treatment.

There are certain contraindications to the use of methotrexate:

• Pregnancy and breastfeeding.

It is crucial not to consider pregnancy during methotrexate treatment, in the month or ovulatory cycle following its cessation for women, or within 3 months for men. Pregnancy is strongly discouraged during treatment. If a pregnancy occurs, it is important to immediately stop the treatment and inform your doctor. Indeed, methotrexate is a teratogenic drug that can lead to fetal death, miscarriage, or congenital abnormalities. Similarly, breastfeeding is contraindicated during treatment as methotrexate can pass into breast milk and be toxic to the baby.

• Use of other medications.

Some drug combinations are prohibited with methotrexate as they could potentially increase its concentration in the blood and render it toxic. Before taking a new medication, it is crucial to check with your doctor if it is compatible with methotrexate.

• Vaccines.

Most vaccines can be administered during treatment with methotrexate, with the exception of "live" vaccines such as the yellow fever vaccine. Indeed, methotrexate is an immunosuppressant associated with a risk of severe infections. Vaccination in these patients could pose a risk of developing a disease. If necessary, live vaccines should be administered at least three weeks before starting the treatment.

Note: It is essential to maintain regular follow-ups with your doctor and dermatologist throughout the duration of the treatment, without forgetting to carry out the prescribed blood tests.

Adverse effects are rare, but it's important that you are informed about them. Among the possible adverse effects are:

• A decrease in red blood cells, white blood cells, or platelets.

• A liver condition, manifesting in individuals with a liver weakened by alcohol consumption, overweight, or a history of viral infections.

• Rarely, symptoms such as coughing, fever, or shortness of breath may occur.

• Nausea and abdominal heaviness can occur, typically in a moderate manner.

• Erosions resembling canker sores can form in the mouth or on the skin.

• At times, one may experience feelings of fatigue or a decrease in libido.