Methotrexate for Psoriasis

Methotrexate. This medication slows down the build-up of dead skin cells by interfering with DNA and by suppressing the immune system. Methotrexate is also used to treat cancer. The doses used to treat psoriasis are much smaller than those used in cancer treatment. A supplement of folic acid (a B vitamin) may be taken at the same time. Methotrexate is very effective for people with widespread psoriasis that does not respond to ultraviolet light treatment or to medications applied to the skin. It is also effective for psoriatic arthritis. Skin improvement usually begins within several weeks of starting treatment. Maximum improvement is usually seen within 2 to 3 months. Medications applied to the skin may be used to treat any remaining plaques. If psoriasis still does not clear completely, or if the drug dose must be lowered to reduce side effects, methotrexate may be combined with UVB or PUVA phototherapy or with another medication, such as a retinoid. People taking methotrexate must be closely monitored. The drug can cause liver damage. It can also decrease the body's production of red and white blood cells and platelets. Regular blood tests should be done to check the blood count and liver and kidney function. A periodic liver biopsy may also be recommended because the drug's effects on the liver may not show up on blood tests. People who have liver disease or anemia should not take methotrexate. Methotrexate can cause birth defects. It cannot be used by pregnant women, women planning to become pregnant, or their male partners.