Quetiapine as an alternative to clozapine in the treatment of dopamimetic psychosis in patients with Parkinson's disease.

There are many difficulties associated with the late stages of Parkinson's disease (PD), but psychosis and agitation may be the most disturbing for both patients and care givers, and often precipitate the pivotal decision for long-term nursing home placement. While the addition of antipsychotic drugs or the withdrawal of antiparkinsonian drugs may improve the behavioral problem, these strategies usually worsen the motor difficulties. Clozapine has been studied in PD for over a decade, and while it appears to be effective, there are safety and tolerability concerns associated with it. In addition, in New Jersey, Medicaid no longer pays for the home blood draws that are required for home-bound patients. This led to a situation in which we had patients who needed to stop clozapine and begin an alternative therapy. Because quetiapine seems particularly well suited to patients with PD based on in vitro and in vivo studies we have begun to try this medication in PD patients who need to stop clozapine. This article reports three case histories of patients with PD, confusion and dopamimetic psychosis who had been previously managed with clozapine and who were successfully switched to quetiapine. At doses from 12.5 to 150 mg/day quetiapine was well tolerated, resulting in behavioral improvement and no real increase in parkinsonism. These case histories raise the possibility that quetiapine may represent a viable alternative to clozapine in PD patients with dopamimetic psychosis and behavioral disturbances.