Introduction: Once-daily extended release quetiapine fumarate (quetiapine XR) monotherapy was evaluated in major depressive disorder (MDD).Method: This was an 8-week (6-week randomized-phase; 2-week drug-discontinuation/tapering phase), double-blind, parallel-group, placebo-controlled study. The primary outcome measure was Montgomery-Åsberg Depression Rating Scale (MADRS) total score randomization-to-Week 6 change. Other assessments included the Hamilton Rating Scale for Depression, the Hamilton Rating Scale for Anxiety, and adverse events (AEs).Results: 723 patients were randomized: 182, 178, 179, and 184 to quetiapine XR 50, 150, 300 mg/day, and placebo, respectively. At Week 6, significant reductions occurred in MADRS score with quetiapine XR 50 mg/day (−13.56; P<.05), 150 mg/day (−14.50; P<.01) and 300 mg/day (−14.18; P<.01) versus placebo (−11.07); at Day 4, reductions for quetiapine XR (titrated to 50 or 150 mg/day according to dose group) versus placebo (−2.9) were: −4.7 (P<.01), −5.2 (P<.001), and −5.1 (P<.001), respectively. At endpoint, MADRS response (≥50% reduction in score) was 42.7% (P<.01), 51.2% (P<.001), and 44.9% (P≤.001) for quetiapine XR 50, 150, and 300 mg/day, respectively; 30.3% for placebo. Overall, quetiapine XR 150 mg/day provided consistently more positive secondary efficacy results than 50 mg/day and 300 mg/day versus placebo. The most common AEs in quetiapine XR-treated patients were dry mouth, sedation, somnolence, headache, and dizziness.Conclusion: In patients with MDD, quetiapine XR monotherapy (50/150/300 mg/day) is effective in reducing depressive symptoms, with improvement from Day 4 onwards. Safety and tolerability were consistent with the known profile of quetiapine.
