Purpose: To evaluate the safety and efficacy of risperidone in patients with Parkinson's disease (PD) who are experiencing significant dopamine-induced psychosis.
Patients and methods: Seventeen patients (median age, 72 yrs) participated in this 12-week, open pilot study receiving 0.5 to 3 mg oral risperidone per day. Maintenance antiparkinsonian medication was continued throughout, although psychotropic medication was discontinued. EFFICACY RESULTS: Risperidone produced a substantial improvement in psychotic symptoms, shown on the mean total positive subscale score on the Positive and Negative Syndrome Scale (PANSS) by a 30% improvement (-3.1 decrease) after 1 week and a 66% improvement (-6.8 decrease) at end point. This improvement was most evident in the items delusions, hallucinatory behavior, and suspiciousness/persecution. Risperidone also achieved significant improvement from baseline in Clinical Global Impression (CGI)-severity and CGI-improvement (p < 0.001, Page test). Risperidone treatment did not adversely affect symptoms specific to Parkinson's disease, as assessed by the Unified Parkinson's Disease Rating Scale (UPDRS). SAFETY RESULTS: Sixteen patients reported at least one adverse event, but only two patients withdrew as a result of adverse events. No significant changes or clinically relevant abnormalities were observed in laboratory parameters or vital signs.
Conclusion: Short-term use of risperidone (mean dosage, 1.1 mg per day) improves the psychopathology of patients with PD who have dopamine-induced psychosis without adversely affecting the symptoms of PD. Higher doses and long-term use were not addressed in this study and may be precluded by extrapyramidal side effects.