Background: Several studies indicate that ketamine has rapid antidepressant effects in patients with treatment-resistant depression (TRD). The extent to which repeated doses of ketamine (versus placebo) reduce depression in the short and long term among outpatients with TRD and chronic, current suicidal ideation remains unknown.
Methods: Twenty-six medicated outpatients with severe major depressive disorder with current, chronic suicidal ideation were randomized in a double-blind fashion to six ketamine infusions (0.5 mg/kg over 45 minutes) or saline placebo over three weeks. Depression and suicidal ideation were assessed at baseline, 240 min post-infusion, and during a three-month follow-up phase.
Results: During the infusion phase, there was no differences in depression severity or suicidal ideation between placebo and ketamine (p = 0.47 and p = 0.32, respectively). At the end of the infusion phase, two patients in the ketamine group and one in the placebo group met criteria for remission of depression. At three-month follow-up, two patients in each group met criteria for remission from depression.
Limitations: Limitations include the small sample size, uncontrolled outpatient medication regimens, and restriction to outpatients, which may have resulted in lower levels of suicidal ideation than would be seen in emergency or inpatient settings.
Conclusions: Repeated, non-escalating doses of ketamine did not outperform placebo in this double-blind, placebo controlled study of patients with severe TRD and current, chronic suicidal ideation. This result may support our previously published open-label data that, in this severely and chronically ill outpatient population, the commonly used dose of 0.5 mg/kg is not sufficient.
Keywords: Ketamine; Repeat-doses; Suicidal ideation; Treatment-resistant depression.
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