Sex and Age Differences in Ketamine Efficacy and Safety in Chronic Pain Alleviation

<b>Background:</b> Ketamine use for chronic pain and depression has increased worldwide, but sex differences in its efficacy and safety have been little studied; this study examines existing evidence to address this gap. <b>Methods:</b> A prospective, multicenter, one-year observational study in 585 chronic pain patients was performed; 256 patients had one administration of ketamine and 329 had two or more. The primary outcome looked at was mean pain intensity (0-10), assessed every month for 1 year by telephone. Secondary outcomes included measures of depression and anxiety (assessed using the Hospital Anxiety and Depression Scale), quality of life (evaluated with the 12-item Short Form Health Survey), total ketamine dosage, reported adverse effects, and concomitant treatments. Platform of Clinical Investigation, No sex or age differences were observed in ketamine efficacy in terms of pain (mean variation in women vs. men; effect size -0.5 (95% confidence interval -0.6 to -0.4) vs. -0.5 (95% confidence interval -0.7 to -0.3), <i>p</i> = 0.248) or the evolution of anxiety (<i>p</i> = 0.135) among the 585 patients. Women reported more adverse events than men (19% vs. 13%, <i>p</i> = 0.002). In the subgroup of 329 patients, no differences were observed in any variables, but a single ketamine administration may be more useful in men than in women (<i>p</i> = 0.032), especially in younger men (<i>p</i> = 0.045). <b>Conclusions:</b> Repeated ketamine administration displayed no sex or age differences in efficacy in the treatment of pain, anxiety or depression.