To evaluate quetiapine XR as adjunct to ongoing antidepressant therapy in patients with MDD showing inadequate response to antidepressant treatment.

Data were analysed from two 6-week, multicentre, double-blind, randomised, placebo-controlled studies (D1448C00006; D1448C00007), prospectively designed to be pooled. Outpatients received adjunctive quetiapine XR 150mg/day (n=309), 300mg/day (n=307), placebo (n=303). Primary endpoint: change at Week 6 in MADRS total score. Other assessments included: MADRS individual item scores, HAM-A total scores, MADRS response and remission; AE reporting.

Quetiapine XR 150mg/day and 300mg/day (p< 0.001) reduced MADRS total scores versus placebo at Week 6 (-14.5, -14.8, -12.0) and Week 1 (-7.8, -7.3, -5.1). Subgroup analyses showed the therapeutic effect of quetiapine XR was neither limited to nor driven by factors such as gender or antidepressant class (SSRI/SNRI). Quetiapine XR demonstrated consistent improvements in individual MADRS items: 150mg/day and 300mg/day significantly improved 4/10 and 7/10 items at Week 6 versus placebo. At Week 6, MADRS response (≥50% decrease in total score) was 53.7% (p=0.063), 58.3% (p< 0.01) versus 46.2%; MADRS remission (total score ≤8) was 35.6% (p< 0.01), 36.5% (p< 0.001) versus 24.1% for quetiapine XR 150mg/day and 300mg/day and placebo, respectively. Quetiapine XR 150mg/day and 300mg/day improved HAM-A total scores versus placebo at Week 1 (-4.8 [p< 0.001], -4.2 [p< 0.01], -3.0) and Week 6 (-8.9 [p< 0.01], -9.1 [p< 0.001], -7.3). AEs (≥10%) were dry mouth, somnolence, sedation, dizziness, fatigue, constipation and headache with quetiapine XR.

In patients with MDD and an inadequate response to antidepressant therapy adjunctive quetiapine XR is effective and generally well tolerated.