D. Fagan et al., A DOSE-RESPONSE STUDY OF THE EFFECTS OF INHALED NITROUS-OXIDE ON PSYCHOLOGICAL PERFORMANCE AND MOOD, Psychopharmacology, 116(3), 1994, pp. 333-338
In this five-period randomised double-blind crossover study, 12 health
y volunteers inhaled mixtures of nitrous oxide at concentrations of 0%
(placebo); 5%, 10%; 20% and 40% in oxygen. Each concentration was inh
aled for about 1 h, each period being on a separate day. The effects o
f nitrous oxide were measured using a comprehensive battery of perform
ance tests including measures of attention, psychomotor function, memo
ry and cognition. Mood was assessed with visual analogue scales. All t
ests except critical flicker fusion showed substantial effects at the
highest does (40%). No measure showed evidence of change at the lowest
concentration (5%). Several measures showed significant impairment at
10%, viz: digit-symbol substitution, choice reaction time (latency an
d total), tapping, and continuous attention. Subjects felt dizzy and m
uzzy on nitrous oxide, but no significant effect was seen on the Alert
-Drowsy VAS. The dose-response profiles of the various tests showed su
bstantial differences. Thus tapping was virtually linear, while choice
reaction motor time and body sway showed steeply accelerating impairm
ent with increasing dose. These results indicate that comparisons of p
rofiles of drug-induced change must take into account the variable eff
ects of dose before interpretations in terms of specific drug effects
can be made.