This was a phase II, multicenter, double-blind, randomised, placebo-controlled, parallel-arm study in which 67 TRD patients were given intravenous ketamine (0.5mg/kg of body weight) or placebo three or two times a week for up to four weeks [4].
The primary outcome measure was the change in MADRS from baseline to day 15. In the twice-a-week, group the mean change in MADRS at day 15 was -18.4 for ketamine which showed statistical significance when compared with the placebo mean change of -5.7 (p<0.001) [4]. The thrice-a-week group mean change in MADRS at day 15 was -17.7 for ketamine also showing statistical significance when compared with the placebo mean change of -3.1 (p<0.001)[4]. There was no overall statistical significance between the two dosing regime scores themselves when compared.
The trial concluded that both twice- or thrice-a-week intravenous dosing regimes of 0.5mg/kg ketamine showed sustained antidepressant efficacy over 15 days in TRD patients but did not differ in the degree of their effects. With it being more logistically and economically viable to use fewer doses in addition to questions that remain of the longer time side effects, this trial highlights the potential of a twice-a-week dosing regime for 0.5kg/mg intravenous ketamine warranting further study.