Introduction Predictors of treatment response to intravenous ketamine
remain unclear in patients with treatment-resistant depression (TRD); therefore,
this study aimed to clarify these predictors using the US National Institutes of
Health database of clinical trials.
Methods Data from a placebo-controlled, double-blind, randomized
controlled trial were used to assess the efficacy of intravenous ketamine in
adult patients with TRD (NCT01920555). For the analysis, data were used from the
participants who had received therapeutic doses of intravenous ketamine
(i. e., 0.5 and 1.0 mg/kg). Logistic and multivariable
regression analyses were conducted to explore the demographic and clinical
factors associated with response to treatment or changes in the Hamilton
Depression Rating Scale 6 items (HAM-D-6) total score.
Results This study included 31 patients with TRD (13 women;
mean±standard deviation age, 48.4±10.9 years). Logistic
regression analysis showed that the age of onset was positively correlated with
treatment response after three days of ketamine administration
(β=0.08, p=0.037); however, no association was observed
between treatment response and age, sex, baseline HAM-D-6 total score, or
dissociative score assessed with the Clinician-Administered Dissociative States
Scale 40 min after ketamine infusion. Multiple regression analysis showed that
no factors were correlated significantly with the percentage change in the
HAM-D-6 total score three days after ketamine administration.
Discussion Later disease onset correlates with a better treatment response
three days after ketamine infusion in patients with TRD. Glutamatergic signal
transmission may be impaired in patients with an earlier onset of depression,
resulting in decreased neuroplasticity, which diminishes ketamine response.