The Use of Low-dose Oral Methotrexate in the Treatment of Polymyositis and Dermatomyositis.

The objective of this study was to evaluate the efficacy of low-dose oral methotrexate (MTX) in improving muscle strength and reducing the corticosteroid requirement of patients with polymyositis (PM) and dermatomyositis (DM). The method used was a retrospective chart review of our clinic's PM/DM cohort, Between September 1989 and May 1993, 12 of 53 patients with PM/DM received low-dose oral MTX (mean maximum dose 14.4 +/- 1.2 mg/wk, range 7.5-20 mg/wk). A significant increase in strength coupled with a fall in prednisone requirement (42.5 +/- 5.8 mg/d to 13.0 +/- 5.4 mg/d) was seen during the mean follow-up time of 24.0 +/- 4.3 months of MTX therapy. The number of flares per year fell from 1.00 +/- 0.35 before oral MTX institution to 0.07 +/- 0.05 during oral MTX therapy. Toxicity was minimal. Three patients were able to stop corticosteroids altogether. Low-dose oral MTX therapy should be considered early in the treatment course of patients with PM/DM to improve strength and lower the required dose of corticosteroids.