Levomilnacipran ER vs. Adjunctive Quetiapine for Adults With Inadequate Relief With SSRIs in MDD

1. Study Design 1) An 8-week, randomized rater blinded parallel group, 2-arm trial 2) Trial duration - 9 weeks 3) Drug doses * Levomilnacipran ER; Switching to a flexible dose regime of levomilnacipran ER 40-120 mg/day after initial dose of 20mg. * Quetiapine XR; Adjunct a flexible dose regimen of quetiapine XR 150-300 mg/day after initial dose of 50mg. 2. Objective 1) To compare the efficacy and tolerability of switching to levomilnacipran ER (40-120 mg/d) versus augmentation with quetiapine XR 150-300 mg/day to the patients' existing treatment for patients with inadequate relief on generic SSRIs in patients with MDD. 2\) To examine the response following the switch from generic SSRI to levomilnacipran ER and augmentation with quetiapine XR. 3\) To examine changes in neurocognitive and apathy measures after switching from SSRI to levomilnacipran ER and after augmentation with quetiapine XR in MDD