Clozapine for the treatment of psychosis in Parkinson's disease: a review.

The occurrence of psychosis is frequent during the evolution of Parkinson's disease. The reduction of therapeutics or the use of classical neuroleptics may improve the symptoms, but usually worsens parkinsonism. Clozapine is an atypical neuroleptic with only few extrapyramidal effects, which has been proposed at low dose in this indication since 1985. A review of the literature, about more than 200 patients shows good results in approximately 90% without worsening of extrapyramidal symptoms. Some patients even noted an improvement of their motor state while treated by clozapine alone or as dopatherapy was secondarily increased. More controversial results were obtained in demented or depressed patients. Sedation is one of the most frequently encountered side-effect but rarely necessitates the withdrawal of clozapine. Even if the risk of agranulocytosis is slight, regular blood cell counts must be done.