Effect of amantadine in essential tremor: a randomized, placebo-controlled trial.

There is a need for new medication for essential tremor (ET). Preliminary evidence suggests that amantadine may be effective in the treatment of ET. We studied the effects of amantadine in a double-blind, cross-over, placebo-controlled trial in ET patients. Sixteen patients with ET received amantadine 100 mg b.i.d. and placebo for 15 days, with a 1-week wash-out period between treatments. Major evaluation outcomes consisted of a tremor clinical rating scale, accelerometric recordings, and a self-reported disability scale obtained before drug intake and on study days 1 and 15 of each treatment period. A two-way repeated measures analysis of variance (treatment, time) was applied. Any P value < 0.05 was considered significant. On day 15, amantadine did not demonstrate any significant efficacy in reducing tremor with respect to baseline in any tremor measures. An increase in postural tremor as an adverse effect of amantadine was referred by 37.5% of patients. Results from the present trial indicate amantadine at 100 mg b.i.d. is not effective as a treatment for ET.