Eleven patients with
Parkinson's disease (PD) and acute
psychosis received flexible doses of
quetiapine between 25 and 300 mg/day based on clinical response and tolerance. Ten patients were receiving
dopaminergic agents at baseline. Serial efficacy ratings (Brief Psychiatric Rating Scale, Clinical Global Impressions Scale), neuromuscular symptom assessments (Abnormal
Involuntary Movement Scale, Simpson-Angus Scale, Unified Parkinson's Disease Rating Scale [UPDRS]), and adverse events monitoring were performed for up to 52 weeks. The patients had moderate
hallucinations and/or delusions at baseline before the initiation of
quetiapine. Nine of the 11 patients completed at least 12 weeks of treatment.
Quetiapine was well tolerated in all but one patient, who became dizzy within the first week and withdrew from the study. Ten patients presented with moderate
visual hallucinations.
Quetiapine was markedly effective in controlling
visual hallucinations in six of these patients. Symptoms of
paranoia or delusions were less responsive to
quetiapine. Four patients withdrew because of adverse events or comorbid medical problems, two withdrew because of a lack of efficacy, and five completed 52 weeks of treatment. The introduction of
quetiapine did not exacerbate parkinsonian symptoms. Motor dysfunction, as measured by the UPDRS, revealed a slow, gradual worsening consistent with the progression of PD. Atypical
antipsychotic medications such as
quetiapine have a reduced likelihood of causing adverse
drug-induced
parkinsonism and therefore a possible role in treating psychotic symptoms in patients with PD.