Antipsychotic Effects of Quetiapine in Naturalistic Long Term Follow Up Study

OBJECTIVE This study aimed to examine the effectiveness of quetiapine and the effects of dosage relates to its effectiveness on schizophrenia and schizoaffective disorder in a naturalistic setting in Korean people. METHODS This study was a 24-week, open-label, non-comparative, naturalistic study of quetiapine in patients diagnosed with schizophrenia and schizoaffective disorder according to DSM-IV. We stratified the patients into mild [(clinical global impression severity (CGI-S) <4 at baseline)] and severe groups (CGI-S >/=4 at baseline). We investigated the response rate, defined as clinical global impression improvement (CGI-I) </=2, in the severe group and the aggravation rate in the mild group using the last-observation-carried-forward (LOCF) and the Kaplan-Meier method (K-M). RESULTS During the 24 weeks, 151 (18.4%) of the participants dropped out of the study. There was a significant decrease in the mean CGI-S score, from 4.5+/-1.1 at baseline to 2.8+/-1.1 at 24 weeks. The response rate of severe group was 54.5% (estimated by LOCF) and 73.3% (K-M estimated) at 24 weeks. All patients who completed the study had taken a mean quetiapine dosage of 507.9+/-245.9 mg daily. The decrease of CGI-S score in high-dose group (the maximum dose was 750 mg/d or above) was statistically significant than that in recommended-dose group (the maximum dose was less than 750 mg/d). CONCLUSION This study demonstrated the long-term effectiveness of quetiapine in the treatment of schizophrenia and schizoaffective disorder in a naturalistic setting in Korean people. This study suggests that higher than recommended quetiapine dosages could be more effective in some patients.