Low-dose clozapine in the treatment of levodopa-induced mental disturbances in Parkinson's disease.

Delusions and other manifestations of psychotic behavior are common side effects in Parkinson's disease (PD) patients chronically treated with dopaminergic drugs. Clozapine, a dibenzodiazepine derivative, is an antipsychotic drug largely devoid of extrapyramidal side effects. We evaluated the effects of low doses of clozapine on the mental and motor functions in PD patients requiring antipsychotic treatment. Twenty-seven PD patients taking dopaminergic drugs and who had psychotic behavior received clozapine at 12.5 to 75 mg/d. Fifteen patients received clozapine for 1 to 11 months (mean, 6.8 months) and seven received it for 12 to 24 months (mean, 18 months). No patient exhibited motor deterioration, and the psychotic features disappeared immediately, allowing discontinuation of clozapine after several months in 10 patients. Fifteen patients are still receiving clozapine and are free of psychiatric symptoms. The clozapine treatment was discontinued after 5 days (25 mg/d) in two patients because of somnolence. No patient developed neutropenia. Clozapine in low doses is effective in the treatment of drug-induced delusions and hallucinations in PD.