Ketamine augmentation for outpatients with treatment-resistant depression: Preliminary evidence for two-step intravenous dose escalation.

Objective: Preliminary evidence supports the safety and efficacy of subanesthetic ketamine as an experimental antidepressant, although its effects are often not sustained beyond one week. Studies are lacking that have examined the sustained effects of escalating ketamine doses as augmentation in outpatients with treatment-resistant depression. Therefore, the aims of this study were twofold: (1) to assess the safety and antidepressant efficacy of two-step, repeated-dose ketamine augmentation and (2) to assess the duration of ketamine's antidepressant efficacy as augmentation to ongoing antidepressant pharmacotherapy for 3 months after the final infusion.