Human Performance Following Antihistamine Administration

The objective of this research was to evaluate the effects of two antihistamines on a range of cognitive performances. Diphenhydramine was chosen because of its purported nervous system effects, while terfenadine was chosen because of its purported lack of similar effects. Six male subjects were trained on the nine task Naval Medical Research Institute Performance Assessment Battery NMRIPAB until performance accuracy was at least 90 for three consecutive sessions. They were subsequently administered either 60 mg of terfenadine, 100 mg of diphenhydramine, or placebo in a mixed order. Each condition was replicated three times. NMRIPAB sessions were conducted 1 hour, 2 hours, and 3 hours post drug administration. Diphenhydramine produced selective decreases in the accuracy of responding on five of the nine NMRIPAB tasks. It also produced increases in response latency in two of the nine tasks. The majority of diphenhydramine effects occurred during the second or third hour of testing, which is in conformance with the reported pharmacokinetics of the compound. Terfenadine did not produce consistent effects on any task. Each subject exhibited differing patterns of task sensitivity to diphenhydramine administration.