Identification of an optimal dose of intravenous ketamine for late-life treatment-resistant depression: a Bayesian adaptive randomization trial

• Published in: Neuropsychopharmacology (New York, N.Y.) Vol. 47; no. 5; pp. 1088 - 1095
• Main Authors: Lijffijt, Marijn, Murphy, Nicholas, Iqbal, Sidra, Green, Charles E., Iqbal, Tabish, Chang, Lee C., Haile, Colin N., Hirsch, Lorna C., Ramakrishnan, Nithya, Fall, Dylan A., Swann, Alan C., Al Jurdi, Rayan K., Mathew, Sanjay J.
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 01.04.2022
• Subjects: Bayes Theorem; Bayesian analysis; Clinical trials; Depression; Depressive Disorder, Treatment-Resistant - drug therapy; Double-Blind Method; Double-blind studies; EEG; Female; Humans; Infusions, Intravenous; Intravenous administration; Ketamine; Ketamine - therapeutic use; Mental depression; Midazolam; Middle Aged; Random Allocation; Response rates; Treatment Outcome; Treatment resistance
• ISSN: 0893-133X; 1740-634X; 1740-634X
• DOI: 10.1038/s41386-021-01242-9

Evidence supporting specific therapies for late-life treatment-resistant depression (LL-TRD) is necessary. This study used Bayesian adaptive randomization to determine the optimal dose for the probability of treatment response (≥50% improvement from baseline on the Montgomery-Åsberg Depression Rating Scale) 7 days after a 40 min intravenous (IV) infusion of ketamine 0.1 mg/kg (KET 0.1), 0.25 mg/kg (KET 0.25), or 0.5 mg/kg (KET 0.5), compared to midazolam 0.03 mg/kg (MID) as an active placebo. The goal of this study was to identify the best dose to carry forward into a larger clinical trial. Response durability at day 28, safety and tolerability, and effects on cortical excitation/inhibition (E/I) ratio using resting electroencephalography gamma and alpha power, were also determined. Thirty-three medication-free US military veterans (mean age 62; range: 55-72; 10 female) with LL-TRD were randomized double-blind. The trial was terminated when dose superiority was established. All interventions were safe and well-tolerated. Pre-specified decision rules terminated KET 0.1 (N = 4) and KET 0.25 (N = 5) for inferiority. Posterior probability was 0.89 that day-seven treatment response was superior for KET 0.5 (N = 11; response rate = 70%) compared to MID (N = 13; response rate = 46%). Persistent treatment response at day 28 was superior for KET 0.5 (response rate = 82%) compared to MID (response rate = 37%). KET 0.5 had high posterior probability of increased frontal gamma power (posterior probability = 0.99) and decreased posterior alpha power (0.89) during infusion, suggesting an acute increase in E/I ratio. These results suggest that 0.5 mg/kg is an effective initial IV ketamine dose in LL-TRD, although further studies in individuals older than 75 are required.