The "Seroquel" Outcomes Study (SOS): Efficacy and tolerability of quetiapine in a long-term, naturalistic study of patients with schizophrenia.

Objective. The "Seroquel" Outcomes Study (SOS) aimed to assess the efficacy and tolerability of quetiapine in patients with schizophrenia in the clinical practice setting. Methods. A 6-month, non-comparative, open-label study in adults with schizophrenia in a standard care setting in Spain. Outpatients received flexibly dosed quetiapine. Efficacy was evaluated using the Brief Psychiatry Rating Scale (BPRS) and the Clinical Global Impression (CGI) scale. BPRS response was defined as≥30% decrease from baseline. Tolerability was assessed using the Simpson-Angus Scale (SAS) and a modified Udvalg for Kliniske Undersogelser (UKU) side-effects scale. Results. A total of 2029 patients enrolled. Significant changes from baseline to Month 6 were recorded for BPRS total and subscale scores (P<0.001). Compared with doses of≥600 mg/day, doses of<400 mg/day were a strong predictor of a lower response rate (OR 0.62; 95% CI: 0.48, 0.82) and higher withdrawal rate (OR 3.3; 95% CI: 2.5, 4.4). Mean change in weight was minimal (+0.4 kg). Somnolence (26.7%), asthenia (12.5%), and constipation (9.8%) were the most common adverse events. Conclusion. Quetiapine was found to improve symptoms of schizophrenia, as indicated by a significant decrease in BPRS scores, and was well tolerated by patients in clinical practice.