Ketamine for major depressive disorder during an inpatient psychiatric admission: Effectiveness, adverse events, and lessons learned*,**

Objective: Most studies examining the efficacy of ketamine for Major Depressive Disorder (MDD) have been conducted in outpatient or mixed inpatient/outpatient settings. Less is known about effectiveness and tolerability of ketamine for psychiatrically hospitalized patients. Efficacy and tolerability data from a naturalistic sample of acute inpatients may help inform institutions considering ketamine therapy for inpatient services. Methods: We performed a retrospective chart review of inpatients with non -psychotic MDD treated during the initial 3 years of a ketamine infusion program. Treatment effectiveness was defined using change in Montgomery Asberg Depression Rating Scale (MADRS) scores over five infusions. MDD treatment response was defined by a 50 % reduction of MADRS score, and remission was defined as MADRS score <= 10 at any point during the treatment. We also report the frequency of adverse events. Results: 41 patients with MDD were treated and had outcome data. 19 patients (46.5 %) met criteria for response and 15 patients (26.5 %) met criteria for remission during treatment. Four patients (10 %) had adverse psychological or behavioral outcomes. Limitations: MADRS scales were administered by psychiatrists, psychologists, and trainees in each discipline who did not undergo standardized training in scale administration. Consistent data regarding the race/ethnicity of the patients was not available. Conclusion: Twice weekly racemic ketamine infusion is an effective treatment option for patients hospitalized with MDD. Unmonitored or at home ketamine therapy may pose substantial risks.