Dexamethasone mimicks the antimotion sickness effects of amphetamine and scopolamine

Based on preliminary suggestions that individual differences in susceptibility to stressful motion might be related to physiological differences in responses of the hypothalamic-pituitary-adrenal axis, we tested the efficacy of dexamethasone and metyrapone in subjects exposed to cross-coupled accelerative semicircular canal stimulation on a rotating chair. Subjects given 0.5 mg of dexamethasone every 6 h for 48 h could endure 80% more stressful motion (P = 0.03) in a within-subjects design study, whereas, no improvement followed treatment with 750 mg of metyrapone[correction of metryapone] every 4 h for 24 h. The efficacy of dexamethasone might be explained in terms of its neurochemical actions on several neurotransmitter systems which are also modulated by such classical antimotion sickness drugs as amphetamine and scopolamine. Because dexamethasone induces adaptive changes within the central nervous system it may prove superior to scopolamine and amphetamine which possess significant side effects, are short acting, and rapidly tolerated.