Effects of loratadine and cetirizine on actual driving and psychometric test performance, and EEG during driving

Sixteen healthy male and female volunteers took part in a 6-way, double-blind cross-over trial to compare the effects of single doses of cetirizine 10 mg, loratadine 10 mg and placebo, with and without alcohol (0.72 g.kg-1, lean body mass). Performance was measured in two repetitions of a psychometric test battery, and a standard, over-the-road driving test. EEG was also measured during driving. Alcohol significantly affected almost every performance measure and altered the EEG energy spectrum during driving whilst the blood concentrations declined from 0.37 to 0.20 mg.ml-1. The effects of cetirizine of on driving performance resembled those of alcohol. It caused the subjects to operate with significantly greater variability in speed and lateral position ('weaving' motion). The effects of alcohol and cetirizine appeared to be additive. Certain cetirizine-placebo differences in subjective feelings and test battery performance were also significant. Loratadine had no significant effect on any performance parameter. It was concluded that cetirizine, but not loratadine, generally caused mild impairment of performance after a single 10 mg dose.