Effects of emedastine and cetirizine, alone and with alcohol, on actual driving of males and females

Emedastine is registered in its country of origin (Japan) as an antihistamine for the indication of seasonal allergic rhinitis. Further research on the drug's sedating properties was needed to secure its registration elsewhere. The present study was designed to compare the effects of emedastine 2 mg and 4 mg twice daily after single and repeated doses, on actual driving performance versus those of cetirizine 10 mg once daily and placebo; and to determine how repeated doses of each drug interact with alcohol to affect driving. Each treatment was administered for 5 days to 19 healthy volunteers (nine men and ten women, aged 21-45 years) according to a four-period double-blind cross-over design. Driving performance was measured in a standardized test between 3 and 4 h after administration of the morning dose on days 1, 4 and 5. Alcohol, sufficient for achieving a blood alcohol concentration of 0.05 g/dl was given before driving on day 5 of each period. Both emedastine doses similarly and significantly impaired driving in every test. The effects of cetirizine were less. They were significant over days 1, 4 and 5 combined, although not separately. Women were more impaired by both drugs. Alcohol increased driving impairment similarly in every condition. Subjects were only able to discriminate the sedating and impairing effects of the first dose of emedastine 4 mg from placebo. Emedastine, in oral doses of 2 mg and 4 mg twice daily, is sedating and impairs driving. The drug could therefore constitute a traffic hazard and its users should be warned accordingly.