Phillips JL, et al. - Researchers assessed the antidepressant efficacy of a single ketamine infusion, a series of repeated ketamine infusions, and prolongation of response with maintenance infusions in 41 participants with treatment-resistant depression. A single-site randomized double-blind crossover comparison of single infusions of ketamine and midazolam (an active placebo control) was completed by the participants. Outcomes revealed cumulative and sustained antidepressant effects with repeated ketamine infusions. Responders showed maintained reductions in depressive symptoms when received once-weekly infusions. Novel data on efficacious administration strategies for ketamine in patients with treatment-resistant depression were gained in this study.