Benztropine versus clozapine for the treatment of tremor in Parkinson's disease.

Four open-label studies have reported beneficial effects of clozapine on the tremor of idiopathic Parkinson's disease (PD). We performed a double-blind crossover trial with a 2-week washout, comparing low-dose clozapine to benztropine for the treatment of tremor in PD. Twenty-two subjects enrolled and 19 completed the study. Benztropine and clozapine were equally effective in improving tremor and the motor score of the United Parkinson's Disease Rating Scale at mean doses of 3.0 and 39 mg/day, respectively. Significant adverse events were experienced with each drug, but leukopenia was not encountered. We conclude that the atypical antipsychotic drug clozapine is helpful in the treatment of tremor in PD and should be considered when all other drug therapies fail.