Cognitive effects of intramuscular ketamine and oral triazolam in healthy volunteers

Abstract

Rationale 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. Objectives The aim of this study was to compare the cognitive effects of ketamine with those of triazolam in healthy volunteers. Methods 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. Results 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. Conclusions 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.

Acute cognitive effects of high doses of dextromethorphan relative to triazolam in humans

“…These effects were consistent with previous studies of the NMDA antagonist ketamine. In previous studies, ketamine significantly decreased episodic word recall, word recognition, and working memory accuracy (Lofwall et al, 2006; Carter et al, submitted). Likewise, the profile of triazolam effects was also consistent with previous studies in that triazolam produced significant impairments in psychomotor and cognitive performance (Carter et al, 2009; Kleykamp et al, 2010; Mintzer and Griffiths, 2002; Reissig et al, 2012).…”

“…Thus, one of the aims of this study was to examine the acute dose effects of high doses of DXM on a variety of different cognitive measures. A second aim was to extend previous findings from our laboratory on the comparative pharmacology and the differential profiles of the cognitive effects of benzodiazepines such as triazolam (Carter et al, 2006, 2007, 2009; Mintzer and Griffiths 2002, 2005) and NMDA antagonists such as ketamine (Carter et al, submitted; Lofwall et al, 2006). On the basis of the results from these previous studies, we hypothesized that the effects of DXM on participants’ subjective ratings of drug effects and of their own cognitive performance impairment would be greater than those of triazolam, whereas the cognitive impairments observed after administration of triazolam would be greater than those observed after DXM.…”

Comparing confidence intervals for Goodman and Kruskal's gamma coefficient

“…so that f(π) = d satisfies the constraints in Equations (4) and (5). For the current study, either u = 0 or u = 2.…”

“…For these studies, sample variance is an important issue. None of these studies reported CIs, three studies [5,6,8] reported standard errors, two studies [3,9] reported p-values pertaining to the null hypothesis γ = 0, and three studies [2,4,7] reported only the estimate.…”

“…[1] Gamma is a frequently used ordinal association measures. Some recent examples of research using γ include computing the association between two methods to estimate maximal oxygen uptake for humans [2] (N = 795); estimating convergent validity of two questionnaires pertaining to physical ability in patients with Colles' fracture [3] (N = 16); estimating inter-rater reliability of behavioural responses in infants [4] (N = 84); assessing the association between constructs in meta-memory [5] (N = 20), [6] (N = 15), [7] (N = 23), [8] (N = 18); and assessing the associations among several variables related to community-based conservation interventions [9] (N = 68). These examples indicate that sample sizes vary strongly across studies, and very small sample sizes, N < 25 say, are not exceptional.…”