Dosing Pattern and Effectiveness of Quetiapine for Schizophrenic Patients Treated with Flexible Doses for 6 Weeks

Chang, Jung Ki; Lee, Jung Sun; Kim, Chang Yoon

Abstract

OBJECTIVE
Recommended dosage of quetiapine for patients with schizophrenia is from 150 mg to 750 mg, which is based on randomized controlled study. But there are trends of increasing quetiapine dosage in clinical practice. Therefore, we evaluated the clinical aspect of schizophrenic patients who took quetiapine by naturalistic non-intervention study.
METHODS
Schizophrenia outpatients in 88 mental hospitals were selected and 170 psychiatrists evaluated Clinical Global Impressions Scale for Severity (CGI-S) before starting quetiapine medication and CGI-S, Clinical Global Impressions Scale for Improvement (CGI-I), quetiapine dosage and medication compliance at 6 weeks after starting quetiapine medication. Overall efficacy and difference of efficacy between drug-naive patients and medication-switch patients were evaluated. We clustered the patients into 4 groups by using cluster analysis with three variables such as quetiapine dose at week 6, baseline CGI-S, and end-point CGI-S. We compared clinical aspect of each cluster with analysis of variance.
RESULTS
841 patients were enrolled. Efficacy of quetiapine was replicated, and improvement rate defined as CGI-I < or =2 was 55.9%. Drug-naive patients show more improvement in CGI-I than medication-switch patients, and efficacy for patients with insufficient treatment was also reported. Dosage for each clustered group was 25-350 mg, 400-500 mg, 600-700 mg and 750-1,500 mg. 750-1,500 mg group shows more decrease in CGI-S than 400-500 mg group and 600-700 mg group.
CONCLUSION
This study suggests that there is a cluster of patients who take more benefits in reducing symptoms and show more compliance in high-dose quetiapine.