Quetiapine

Abstract

Quetiapine is a dibenzothiazepine atypical antipsychotic which has a close pharmacological resemblance to clozapine. In a number of small noncomparative clinical trials, quetiapine has been successfully used in the treatment of psychosis in patients with Parkinson's disease. Psychosis in these patients is caused by current antiparkinsonian drug therapy, the underlying disease pathology or a combination of both factors. In patients with Parkinson's disease with or without previous exposure to antipsychotics, quetiapine reduced psychotic symptoms as measured by a reduction in Brief Psychiatric Rating Scale scores from baseline. Quetiapine was also effective after treatment failure with clozapine, risperidone or olanzapine, and in psychiatrically stable patients who were switched from either clozapine or olanzapine. Motor function was generally maintained in most patients. In 2 of the largest trials, patients with Parkinson's disease reported adverse events such as headache, nausea, orthostatic hypotension, dizziness and diarrhoea after initiation of quetiapine therapy. In two 12-month trials no development or exacerbation of extrapyramidal symptoms (EPS) occurred after the initiation of quetiapine therapy in patients with Parkinson's disease. In another trial, EPS were reported in 3% of patients with Parkinson's disease given quetiapine after treatment failure with another atypical antipsychotic. The incidence of EPS was generally not significantly different between quetiapine (75 to 750 mg/day) and placebo in patients with schizophrenia. Conclusion: If dosage reduction of antiparkinsonian therapy does not alleviate psychotic symptoms in patients with Parkinson's disease, quetiapine may offer an effective alternative to other atypical antipsychotic agents, without compromising motor function. Confirmation of the relative efficacy and low EPS potential of quetiapine in comparative trials with other atypical agents would be beneficial. However, based on the available data quetiapine is a treatment option for the management of this difficult-to-treat patient group.