Atypical Antipsychotic Drugs in the Treatment of Parkinson’s Disease

Parkinson’s disease (PD) patients often develop psychotic symptoms that severely affect quality of life and limit the use of medications to ameliorate motor symptoms. Psychotic symptoms are a major cause for nursing home placement. While these symptoms do not always require treatment, they often do but antipsychotic drugs all share the common pharmacological mechanism of blocking dopamine D2 receptors which may worsen motor problems in this very vulnerable population. Double blind, placebo controlled trials (DBPCT) have shown that clozapine is effective at controlling the psychotic symptoms at doses far below those used in schizophrenia, without worsening motor function, even improving tremor. DBPCT have demonstrated that olanzapine worsens motor function without improving psychosis. Quetiapine has been shown in DBPCT to be free of motor side effects in PD patients but not effective, whereas many open label studies have indicated that quetiapine is effective. The other atypical have been the subjects of conflicting open label reports. The effects of the atypicals in PD psychosis is reviewed.