Methotrexate for Psoriatic Arthritis

Abstract

Methotrexate, a folic acid antagonist, is one of the most commonly prescribed systemic therapies for the treatment of moderate to severe psoriasis as well as psoriatic arthritis, despite a lack of well-designed, double-blind, placebo-controlled studies supporting its efficacy. Methotrexate's anti-inflammatory action is related to an increase in extra-cellular adenosine, which suppresses neutrophil and monocyte actions. Myelosuppression, hepatotoxicity and interstitial pneumonitis are three most worrisome complications of methotrexate therapy. Accepted monitoring of methotrexate therapy includes complete blood count and liver function tests every four to eight weeks. Although dermatologists and rheumatologists often co-manage these patients, monitoring the potential hepatotoxicity of methotrexate differs in these two specialties. An American dermatology consensus conference recommends liver biopsy for certain high-risk groups and after reaching a cumulative dose of 1–1.5 grams. Rheumatologists, because of an assumption of a similar low rate of hepatotoxicity they experience with rheumatoid arthritis, rarely order liver biopsies.