Systemic Medications: Methotrexate

Approved by the FDA in the 1970s for treatment of severe psoriasis, methotrexate was initially used to treat cancer.

In a person with psoriasis, methotrexate binds to and inhibits an enzyme involved in the rapid growth of skin cells and slows down their growth rate.

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Do not take methotrexate if:

  • You are an alcoholic or have alcoholic liver disease, cirrhosis or other chronic liver diseases;
  • You have an immunodeficiency syndrome or an active infectious disease;
  • You are trying to conceive (applies to both men and women), pregnant or nursing;
  • You have an active peptic ulcer;
  • You have significant liver or kidney abnormalities;
  • You have underdeveloped bone marrow, a low white blood cell count, low platelets or significant anemia.

The less common side effects of long-term methotrexate treatment include liver damage and developing reversible liver scarring. The risk of liver damage increases if a person drinks alcohol, has abnormal kidney function, is obese, has diabetes or has had prior liver disease. Years after the drug, in rare occasions, certain types of cancer, such as lymphoma, and bone marrow toxicity have occurred. Methotrexate can cause a reduced white blood cell count increasing infection risk.

Individuals taking methotrexate must have regular blood tests to ensure that the drug is safely processed by the body including the liver, white blood cells and bone marrow. Additionally, the liver must be biopsied at regular intervals.

Pregnancy should be avoided if either partner is taking methotrexate. Men should be off methotrexate at least three months before trying to conceive. Women should wait at least four months after stopping methotrexate to become pregnant.