Effects of fexofenadine, diphenhydramine, and placebo on performance of the Test of Variables of Attention (TOVA)

Abstract

To determine the effects of diphenhydramine 50 mg and fexofenadine 180 mg on cognitive performance using the Test of Variables of Attention (TOVA), and to ascertain whether the TOVA was sufficiently sensitive to differentiate between the effects of these first- and second-generation H1-receptor antagonists on performance. The study used a double-blind, placebo-controlled, randomized, crossover design. Forty-two subjects completed four separate TOVA tests: at baseline and after administration of placebo, diphenhydramine 50 mg, and fexofenadine 180 mg. On each occasion, subjects rated subjective feelings of drowsiness on a visual analog scale (VAS) before taking the TOVA. Compared with placebo, diphenhydramine caused an increased response time (P = 0.0230) and more omission errors (P = 0.0398). Diphenhydramine was also associated with increased drowsiness VAS ratings (P = 0.0065) compared with placebo. Diphenhydramine caused significantly more commission errors than fexofenadine (P = 0.0354). Neither placebonor fexofenadine 180 mg caused significant changes in any TOVA or VAS measurements compared with baseline. Fexofenadine was not statistically different from placebo for any evaluation. The TOVA was sufficiently sensitive to differentiate between the central nervous system effects of fexofenadine and diphenhydramine. Fexofenadine 180 mg had no significant effect on the TOVA measures of performance or on self-reported drowsiness compared with placebo. In contrast, diphenhydramine 50 mg caused significant increases in omission errors and response time on the TOVA and increases in self-reported drowsiness compared with placebo [corrected].