Risperidone treatment of drug-related psychosis in patients with parkinsonism.

Risperidone, a novel neuroleptic with approximately equal D2 and 5HT2A receptor blocking properties, has been used to treat drug-related hallucinations in patients with Parkinson's disease. However, the results of only small numbers of patients have been reported with the drug demonstrating limited usefulness. We report our experience with this drug in 39 patients (25 women and 19 men) with parkinsonism. Monitored clinical data included duration of disease, Hoehn and Yahr score, Mini-Mental State Score, Unified Parkinson's Disease Rating Scale (UPDRS) prior to drug administration and after 3 and 6 months of treatment, and response to treatment. Twenty-three patients with Parkinson's disease had either complete or near-complete resolution of hallucinations whereas an unsatisfactory response (N = 6) or worsening of parkinsonism (N = 6) was noted in 12 patients, only six of whom had Parkinson's disease. Excluding patients with diffuse Lewy body disease, there was no significant worsening of the UPDRS scores after either 3 or 6 months of treatment. The presence of dementia did not predict response to treatment. Our results suggest that risperidone is a useful treatment for hallucinations in patients with parkinsonism.