A preliminary proof-of-concept trial on the effects of ketamine on fatigue: a randomized crossover trial

Fatigue, a prevalent symptom of chronic illness, impacts quality of life. This proof-of-concept, randomized, double-blind, crossover trial assessed the anti-fatigue effects of ketamine (0.5 mg/kg) versus midazolam (0.045 mg/kg), the active comparator.

Ten participants, who were cancer survivors, with fibromyalgia, myalgic encephalomyelitis/chronic fatigue syndrome, or systemic lupus erythematosus, were randomized into Arm 1 (n = 4, Period 1: ketamine to Period 2: midazolam) or Arm 2 (n = 6, Period 1: midazolam to Period 2: ketamine).

The two periods were separately analyzed because of carryover effects with baseline fatigue scores, assessed by the fatigue visual analog scale (VAS), between the study periods (p = 0.03). Looking at changes in fatigue VAS scores from baseline (pre-infusion) to 3 days post-infusion, the ketamine group had a 21.0% decrease in Period 1 and 10.9% in Period 2, while the midazolam group showed a 17.7% decrease in Period 1 and 12.6% in Period 2. We did not observe a statistically significant difference in both periods. The largest fatigue score reduction for the ketamine group was at 1 day post-infusion, at - 38.7% in Period 1.

Despite no statistical significance, a reduction in real-time fatigue scores was observed, which exceeded the 20% efficacy threshold, the primary outcome, in the ketamine arm from pre-infusion to 3 days post-infusion. The carryover effects and the peak reduction in fatigue at 24 hours after ketamine administration suggest that future trials may need to consider a study design without cross-over and an optimal active placebo alternative.