Quetiapine - A review of its use in schizophrenia

Quetiapine, a dibenzothiazepine derivative, is one of several new 'atypical' antipsychotic agents. In preclinical studies, the drug was predicted to have antipsychotic efficacy and a low propensity to induce extrapyramidal effects. Quetiapine has been shown to be effective in the short term (up to 6 weeks) treatment of patients with schizophrenia in several large well designed trials. In general, clinical efficacy is dose related, with maximum effects occurring at a dosage greater than or equal to 250 mg/day. Quetiapine is at least as effective as chlorpromazine and haloperidol, with similar between-treatment improvement in the various rating scales used to assess overall and negative symptoms. Quetiapine is associated with significantly fewer extrapyramidal effects than haloperidol and may have some advantages over chlorpromazine in this regard. There have been no reports of agranulocytosis attributed to quetiapine and the drug did not produce an elevation in serum prolactin levels in patients with schizophrenia. Headache, somnolence and dizziness are common adverse events that are reported more often with quetiapine than with placebo. Quetiapine is associated with small dose-related decreases in total and free thyroxine; however cessation of treatment usually results in reversal of these effects. The drug is also associated with asymptomatic, generally transient elevations in hepatic transaminases. Although the antipsychotic activity of quetiapine has been well demonstrated in 6-week studies, its long term effectiveness, position relative to other atypical antipsychotic agents and efficacy in refractory schizophrenia remain to be fully determined. Nevertheless, on the basis of available data, quetiapine should provide a valuable alternative to classical antipsychotic agents in the short term treatment of patients with schizophrenia.