Treatment of parkinsonian tremor with clozapine.

After preliminary observations on 5 psychotic and 7 nonpsychotic parkinsonian patients had shown unexpected impressive beneficial effects of the atypical neuroleptic clozapine on tremor, an open clinical study including 12 patients was started. Under a dosage-range approximately 25-50 mg/day significant reduction of tremor intensity and tremor related functional disability (CURS, Sweet's scale) was achieved. Akinesia was not deteriorated, initial fatigue disappeared spontaneously. Pharmacological mode of action of clozapine's antitremor effect remains unclear. Its broad receptor binding spectrum with strong antiserotonergic properties might here play a major role.