Folic Acid With Methotrexate In Psoriasis

Psoriasis is an inflammatory condition characterized by overgrowth of superficial cells in your skin. Some patients with psoriasis also develop a crippling form of arthritis. Methotrexate, a medication that inhibits the growth and division of rapidly proliferating cells, is often administered to psoriasis patients with severe skin involvement or arthritis. Since methotrexate interferes with the actions of folic acid, your doctor may advise you to take extra folic acid when you are undergoing treatment with methotrexate.

Folic Acid

Your cells must synthesize new DNA before they can replicate, and they need RNA to produce proteins, enzymes and other important molecules. According to the Linus Pauling Institute at Oregon State University, folic acid acts as a cofactor for two enzymes that manufacture DNA precursors and stabilize new DNA and RNA strands. In order to be useful to your cells, folic acid must itself be activated by yet another enzyme called dihydrofolate reductase.

Methotrexate Actions

A February 2001 review in "Haemotologica" explains that methotrexate ameliorates psoriasis by interfering with dihydrofolate reductase, thereby inhibiting DNA and RNA synthesis and reducing the turnover of rapidly dividing cells in your skin. This same action suppresses the activity of immune cells that generate the inflammation in skin plaques and in the joints of people with psoriatic arthritis. However, methotrexate also interferes with division in other cell populations that normally reproduce quickly, such as your mucous membranes, hair and gastrointestinal tract.

Supplementation

Methotrexate is usually administered once weekly, either orally or by injection. An October 2000 article in "American Family Physician" recommends folic acid supplementation for psoriasis patients to reduce some of the side effects of methotrexate, which include oral inflammation, diarrhea and hair loss. A folic acid dosage of 1 mg daily -- except on the day you take methotrexate -- or 7 mg once weekly is sufficient to furnish your healthy cells with the folic acid they need to function normally.

Considerations

Psoriasis is an autoimmune disease that responds to methotrexate, which interferes with the activity of the B vitamin, folic acid. Dietary sources of folic acid include dark green leafy vegetables, liver, kidney, brewer's yeast, bean sprouts, wheat germ and many flour products, which are routinely fortified with folic acid. Recommended daily allowances for folic acid range from 65 mcg daily for infants to 600 mcg for pregnant women, but the dosage needed to counteract the effects of methotrexate is approximately 1 mg daily. If you are taking methotrexate, follow your doctor's instructions for folic acid supplementation.