The effects of Benadryl and Hismanal on psychomotor performance and perceived performance

Classic antihistamines (H1 antagonists) have sedative effects and can impair psychomotor performance. 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 single oral doses of (1) Benadryl (diphenhydramine)-50 mg, (2) Hismanal-10 mg, and (3) placebo on a battery of 11 cognitive information-processing tasks and performance ratings in 28 healthy men. Performance decrements were seen at 1 h post-Benadryl ingestion on Following Directions (p < 0.05), at 1.5 h on Unstable Tracking (p < 0.05), and at 3 h on serial addition/subtraction (p < 0.05). No decrements in performance were found post-Hismanal. Subjects perceived their performance as poorer following Benadryl ingestion versus placebo and Hismanal for 3 h postingestion (p < 0.05). Results demonstrate performance effects post-Benadryl ingestion for 1 h longer than previously reported. Tasks which demonstrated sensitivity to antihistamines were those which required an element of sustained attention and those which required a visual-motor response.