The effects of Benadryl and Hismanal on mood, physiological measures, antihistamine detection, and subjective symptoms.

The majority of antihistamines have sedative effects; however, it is claimed that Hismanal (astemizole) does not possess central nervous system side effects. A three-factor, repeated measures, double-blind design was used to compare the effects of singl oral doses of 1) Benadryl (diphenhydramine), 50 mg; 2) Hismanal, 10 mg; and 3) placebo, on two mood scales, physiological measures, sleepiness, the ability to detect ingestion of an antihistamine versus placebo, and symptoms in 28 healthy men. Higher tension, greater fatigue, and lower activity levels were reported post-Benadryl (p < 0.05). Lower vigor-activity and higher confusion-bewilderment post-Hismanal and Benadryl were noted 1 h postingestion (p < 0.05), with confusion being lower and activity higher for Hismanal than for Benadryl (p < 0.05). Low vigor-activity, high confusion, and increased sleepiness post-Benadryl persisted for 3 h, while fatigue-inertia persisted for 7 h (p < 0.05). Results suggest that Hismanal is superior to Benadryl for avoidance of subjective effects; however, neither antihistamine was entirely devoid of subjective effects.