A Double-blind, Placebo-controlled Study of Aripiprazole Adjunctive to Antidepressant Therapy Among Depressed Outpatients with Inadequate Response to Prior Antidepressant Therapy (ADAPT-A Study)

Background: We assessed the efficacy of low-dose aripiprazole added to antidepressant therapy (ADT) in major depressive disorder (MDD) patients with inadequate response to prior ADT.

Methods: As per the sequential parallel comparison design, 225 MDD subjects were randomized to adjunctive treatment with aripiprazole 2 mg/day or placebo across two 30-day phases, with a 2:3:3 randomization ratio to drug/drug (aripiprazole 2 mg/day in phase 1; 5 mg/day in phase 2), placebo/placebo (placebo in both phases), and placebo/drug (placebo in phase 1; aripiprazole 2 mg/day in phase 2). Eligible subjects were patients whose MDD was independently deemed 'valid' with SAFER criteria. Subjects had been receiving ADT for ≥8 weeks, and had inadequate response to ≥1 and <4 adequate ADTs in the current episode, as defined by the Antidepressant Treatment Response Questionnaire.

Results: The pooled, weighted response difference between aripiprazole 2 mg/day and placebo in the two phases was 5.6% (p = 0.18; NS). The aripiprazole 2 mg/day-placebo difference on the Montgomery-Asberg Depression Rating Scale pooled across the two phases was -1.51 (p = 0.065; NS). Other secondary endpoint analyses showed nonsignificant pooled differences favoring aripiprazole over placebo. Of the 225 randomized subjects in phase 1, 2 dropped out in both arms, while in phase 2, of 138 phase 1 placebo nonresponders, 9 dropped out on aripiprazole and 5 on placebo. There were only minimal differences in adverse event rates between treatments, except for constipation, weight gain, and dry mouth, more common on aripiprazole.

Conclusions: This study provides clear support for the tolerability of low-dose aripiprazole as an ADT-augmenting agent, with marginal efficacy.