Multi-center, randomized, double-blind, placebo-controlled study of quetiapine extended-release formulation in Japanese patients with bipolar depression

Rationale: Quetiapine fumarate is an atypical antipsychotic indicated for various mental disorders, but it has not been studied in Japanese patients with bipolar depression. Objectives: To evaluate the efficacy and safety of quetiapine XR (extended release) in Japanese patients with bipolar depression. Methods: In this multi-center, randomized, double-blind, placebo-controlled, fixed-dose study of 431 Japanese adults with bipolar I or II disorder, efficacy was determined by analyzing the mean change from baseline in Montgomery-Åsberg Depression Rating Scale (MADRS) total score. Secondary end points included MADRS response and remission rates, Hamilton Depression Scale 17-Item (HAM-D₁₇), and Clinical Global Impressions-Bipolar (CGI-BP) scale scores. Safety was determined by monitoring adverse events and clinical assessments. Results: This study revealed a statistically significantly greater decrease in MADRS total score after 8 weeks of quetiapine XR 300 mg/day monotherapy compared with placebo (− 12.6 vs. − 10.1; p = 0.034). There were also improvements in MADRS response (44.1 vs. 35.6%) and remission (38.0 vs. 26.6%) rates as well as in HAM-D₁₇ and CGI-BP scale scores compared with placebo. In the subgroup analysis of patients with bipolar I or II disorder, the adjusted mean changes in MADRS total score compared to placebo were − 2.3 and − 2.1, respectively. Adverse events occurred in 149 patients (83.2%) receiving quetiapine XR 300 mg/day and in 81 patients (45.8%) receiving placebo. The most common adverse events were somnolence and thirst, which is consistent with the previously reported safety profile. Conclusions: Once-daily monotherapy with quetiapine XR is an effective and well-tolerated treatment for bipolar depression in Japanese patients.