In a pilot trial of six people with bipolar I or II disorder who had been depressed for at least four weeks, two intravenous infusions of arketamine (0.5 mg/kg followed one week later by 1 mg/kg) rapidly reduced depression severity. Depression scores on the Montgomery-Åsberg Depression Rating Scale fell from a baseline mean of 36.66 to 27.83 one day after the first infusion and from 32.0 to 17.66 one day after the second infusion. The drug was well tolerated with almost no dissociation and no manic symptoms. The findings suggest arketamine has rapid-acting antidepressant properties for bipolar depression, consistent with earlier animal research on major depression.
In a small pilot trial, the antidepressant arketamine was compared with placebo for treatment-resistant depression. Ten participants received both arketamine (0.5 mg/kg) and saline one week apart in a randomized, double-blind, crossover design. Depression improved over time, but there was no significant difference between arketamine and placebo. Dissociation and other adverse events were minimal. The study was underpowered, and the authors conclude that arketamine was not superior to placebo but was extremely safe, recommending larger trials with different dosing strategies.