Abstract
More than eleven million U.S. Veterans are at least 65 years of age, an age group of which almost 20% suffers from clinically significant depressive symptoms. Available pharmacological treatments are suboptimal for patients, including veterans, with late-life depression. Ketamine has emerged as a potentially promising rapid-acting therapy for treatment-resistant depression (TRD). However, few studies have examined the safety, tolerability and efficacy of ketamine therapy for older adults with late-life TRD (LL-TRD). This study uses an adaptive randomization design to test the safety, tolerability, efficacy, and durability of three distinct, single sub-anesthetic doses of intravenous (IV) ketamine versus a single dose of active placebo (midazolam) in older depressed veterans. As the study progresses, Bayesian adaptive randomization recalibrates randomization ratios to allocate more participants to conditions demonstrating greater promise and fewer participants to conditions with less promise. Secondary analyses explore clinical and biological moderating and mediating factors of rapid treatment response. Results are expected to inform both the viability of ketamine treatment and optimal dosing strategies for patients with LL-TRD.