Effects of Fexofenadine, Cetirizine and Diphenhydramine on Psychomotor Performance in Adult Healthy Volunteer

ABSTRACT

The present study was conducted to assess and compare the cognitive and psychomotor effects of fexofenadine, a newer second generation antihistamine with cetirizine, diphenhydramine and placebo in 10 healthy adult volunteers in a double blind, randomized cross over study. Following single dose of each drug, the volunteers were subjected to perform a series of tests of cognitive and psychomotor performance at 1, 3 and 6 hours post dose. The test battery consisted of both subjective and objective tests which were further grouped into instrumental and non-instrumental. Instrumental tests included – Simple reaction time (SRT), Multiple Choice ReactionTime Task (MCRT) and Critical Flicker Fusion frequency threshold (CFFT). The tests used in the non instrumental group were- Stanford Sleepiness Scale (SSS), Digit Cancellation Task (DCT), Digit Symbol Substitution Task (DSST) and mental arithmetic tests. Fexofenadine at doses of 120 mg was not significantly different from placebo in any of the tests used. However, as expected for a verum, all the measures were significantly disrupted by diphenhydramine 25 mg upto 6 hours post dose. Cetirizine 10 mg has produced significant subjective somnolence at 3 & 6 hours post dose but without any impairment of objective tests. These results allow the conclusion that fexofenadine at its recommended therapeutic dose of 120 mg is free from impairment effects on aspects of psychomotor function and hence can be used safely. Cetirizine is mildly sedating though it did not impair any of the objective psychometric tests.