Review of quetiapine and its clinical applications in schizophrenia

Preclinical studies have shown that quetiapine (Seroquel, AstraZeneca) is an atypical antipsychotic with many similarities to clozapine. Both placebo-controlled and comparative studies in patients with schizophrenia have demonstrated that quetiapine has long-term efficacy in both positive and negative domains, as well as beneficial effects on affective and cognitive symptoms. Comparative clinical studies confirm that quetiapine is at least as effective as the standard antipsychotics, chlorpromazine and haloperidol and response rates with quetiapine are similar to those reported with other atypical antipychotics. Quetiapine has also demonstrated superior efficacy to haloperidol in partially responsive patients, who can be particularly difficult to treat. Quetiapine has a wide clinical dosing range (150-750 mg/day), although doses of 400 mg or above should be used in patients who do not fully respond to lower doses of the drug. Quetiapine is generally well tolerated with no requirement for routine ECG or blood monitoring and it has minimal effects on weight. Uniquely among other first-line atypical antipsychotics, quetiapine is associated with a placebo-level incidence of EPS and an indistinguishable effect from placebo on plasma prolactin at all doses. Thus, clinicians can confidently increase the dose of quetiapine, without increasing the risk of EPS or hyperprolactinaemia. A number of studies have also shown that quetiapine is well-tolerated and effective in patients who are particularly susceptible to EPS, including elderly and adolescent patients and those with pre-existing dopaminergic pathology, such as Alzheimer's disease and Parkinson's disease. The consistent efficacy in treating all schizophrenic domains and good tolerability, particularly placebo-level EPS, make quetiapine acceptable to patients, as demonstrated in a survey of patient satisfaction. Thus quetiapine is a suitable first-line therapy for the treatment of schizophrenia and psychosis.