Efficacy of quetiapine in patients with bipolar I and II depression: a multicenter, prospective, open-label, observational study

Purpose: To evaluate and compare the therapeutic efficacy of quetiapine in bipolar I and II depression patients in the clinical setting. Patients and methods: This was an 8-week, multicenter, open-label, observational study for bipolar depression. The dosage of quetiapine was flexible, and concomitant medications were permitted on clinician's judgments. A total of 1097 patients were enrolled, and 764 bipolar depression patients who exhibited good therapeutic compliance (>75% compliance rate) were analyzed. Results: Clinical Global Impression-Bipolar scale and Montgomery-Asberg Depression Rating Scale scores were significantly improved at weeks four and eight compared with the baseline scores. At the end of the 8-week study, the response rate was 58.9%, and the remission rate was 42.1%. However, there were no significant differences in the response and remission rates between bipolar I and II disorder (BD-I and BD-II) patients (response rate 60.1% versus 56.3%; remission rate 44.5% versus 37.0%). Montgomery-Asberg Depression Rating Scale score at baseline (beta=0.612, P<0.001), duration of current episode (beta=-0.152, P=0.001), and presence of remission on previous episode (beta=0.111, P=0.012) were significantly associated with improvements in depressive symptoms. Fatigue (16.0%), somnolence (14.9%), and manic/hypomanic switching (0.6% at week four, 0.3% at week eight) were observed throughout the study period. Conclusion: The results of this study suggest that quetiapine improves depressive symptoms in BD-I and BD-II patients with a minimal incidence of manic switching. The therapeutic efficacy of quetiapine increased with time. Quetiapine could be an effective and safe modality for the treatment of BD-I and BD-II.