Cognitive effects of intramuscular ketamine and oral triazolam in healthy volunteers.

Ketamine causes less cognitive impairment than triazolam at doses that produce greater subjective effects, and unlike triazolam, it does not lead to an underestimation of impairment. In a double-blind study with 20 healthy volunteers, ketamine impaired balance only when assessed early, while triazolam impaired psychomotor coordination and divided attention regardless of task order. Triazolam also tended to impair working memory and episodic memory more than ketamine at doses that produced lower subjective effects and higher performance estimates.

Study at a glance

Abstract

Several studies have documented impairments in memory processes as a result of ketamine administration; however, few studies have compared the profile of cognitive effects of ketamine to other drugs. The aim of this study was to compare the cognitive effects of ketamine with those of triazolam in healthy volunteers. Doses of ketamine (0.2, 0.4 mg/kg intramuscular (i.m.)), triazolam (0.2, 0.4 mg/70 kg p.o.), and double-dummy placebos were administered to 20 volunteers under repeated measures, counterbalanced, double-blind conditions. Peak physiological, psychomotor, subjective, and cognitive effects were examined. Ketamine impaired balance when balance was assessed early in the task order, whereas triazolam impaired psychomotor coordination and divided attention irrespective of task order. Triazolam also tended to produce greater effects on working memory and episodic memory tasks than ketamine at doses that produced lower subjective effects and higher estimates of performance. Ketamine produces less cognitive impairment than triazolam at doses that produced greater subjective effects. Thus ketamine does not produce the underestimation of cognitive impairment typically seen with triazolam.