The effects of acute doses of fexofenadine, promethazine, and placebo on cognitive and psychomotor function in healthy Japanese volunteers.

BACKGROUND: Genetic variations in cross-cultural metabolic capability may attenuate the lack of central nervous system effects of fexofenadine.

OBJECTIVE: To compare the pharmacodynamics of fexofenadine and promethazine versus placebo in Japanese volunteers.

METHODS: In this randomized, crossover, double-blind study, 24 subjects received single doses of fexofenadine 60 mg and 120 mg, promethazine 25 mg, and placebo, with a 6-day washout period between treatments. Objective measures included critical flicker fusion, choice reaction time, and a compensatory tracking task. A line analog rating scale evaluated self-rated sedation. A rapid visual information-processing task evaluated vigilance at baseline and at 2 hours.

RESULTS: Fexofenadine was not significantly different from placebo on any test at any timepoint. In contrast, promethazine impaired critical flicker fusion thresholds (F[3,63] = 5.37, P = 0.0023); increased recognition reaction time (F[3,63] = 13.63, P < 0.0001) and total reaction time (F[3,63] = 12.23, P < 0.0001) components of the choice reaction time test; reduced tracking accuracy (F[3,63] = 14.25, P < 0.0001) and increased reaction times to peripheral stimuli (F[3,63] = 9.29, P < 0.0001) in the compensatory tracking task; reduced the number of valid responses (F[3,63] = 14.86, P < 0.0001) and impaired reaction times (F[3,63] = 12.02, P < 0.0001) in the rapid visual information-processing task test; and impaired subjective ratings of sedation (F[3,63] = 7.55, P = 0.0002), compared with placebo.

CONCLUSIONS: A battery of tests sensitive to impairment by promethazine failed to show any negative cognitive or psychomotor effects with fexofenadine 60 and 120 mg. Fexofenadine is an intrinsically non-impairing antihistamine in Japanese subjects.