Medical Health Encyclopedia

Methotrexate (Rheumatrex) is very effective for severe psoriasis. Despite its adverse effects, some experts view methotrexate as the best therapy for widespread plaque psoriasis. It may also be effective for some patients with other severe forms of the disease, including psoriatic arthritis, generalized erythrodermic and pustular psoriasis. For example, one center reported that 80% of patients reported prolonged improvement. Methotrexate appears to be effective in children, but more safety research is needed.

It has the following beneficial properties:

• It interferes with cell reproduction.
• It has anti-inflammatory properties.
• It is one of the few systemic agents proven to help patients with psoriatic arthritis.

It is important to note that the recommended dose is taken weekly, not daily. Fatal toxicities have been reported in people who mistakenly took it once a day.

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Side Effects. Common side effects of methotrexate are nausea and vomiting, rash, mild hair loss, headache, and mouth sores. It may also cause muscle aches. Many of these side effects as well as anemia, a more serious complication are due to folic acid deficiency. Patients should ask their doctor about supplements (generally recommended at 1 to 5 mg of folic acid daily). Patients who experience severe nausea may opt for injections, which are effective and less expensive than oral agents.

More serious complications include the following:

• Liver damage. (In one study, 25% of patients taking methotrexate for five years developed cirrhosis, liver scarring.) People with existing liver problems should not take it, if possible. Regular monitoring for liver toxicity, including blood tests and liver biopsies, is important in patients who take the drug. Timing of biopsies depends on any risk factors for liver damage.
• Toxic effects on bone marrow, which can cause suppression of blood cell production.
• Osteoporosis. (Low doses do not appear to have any significant affect on bone loss, but long-term studies are needed to confirm this.)
• Kidney complications.
• Increased risk for infections, particularly herpes zoster (shingles) and pneumonia. Methotrexate suppresses the immune system and so should be avoided in patients with active infections.
• Lung disease. This side effect can be sudden and severe, and occurs in up to 5% of people who take methotrexate. It deserves special mention. There are five key risk factors for methotrexate-induced lung diseases: age, diabetes, existing rheumatoid involvement in the lung, protein in the urine, and previous use of rheumatoid arthritis drugs called DMARDs (particularly sulfasalazine, oral gold, and d-penicillamine). Patients should report any symptoms, such as coughing or shortness of breath, that might indicate lung injury.
• Severe anemia from folic acid deficiencies. (Folic acid supplements can offset this effect).
• Negative effects on reproduction. In pregnant women the drug can cause miscarriages and birth defects in the offspring. It may impair fertility in men.
• Lymphomas. A few cases have been reported, which are most likely related to the drug's immune-suppressing effects. In most instances, the disease has gone into remission when the drug was stopped. Most studies have found no significant risk for cancers in patients taking methotrexate.
• Radiation recall. An uncommon side effect in patients who have previously been burned by radiation cancer treatments or by sunburns. In such cases, a flare-up of symptoms occurs in the previously affected skin areas.