Cetirizine effects on objective measures of daytime sleepiness and performance.

Sixty healthy men and women with no sleep complaints, 21 to 45 years of age (mean age 28), were randomly assigned to one of five parallel groups that received one of the following: cetirizine 5 mg (n = 13), 10 mg (n = 13), or 20 mg (n = 11); hydroxyzine 25 mg (n = 12); or placebo (n = 11). After one adaptation night in the lab, the subjects' sleep patterns were recorded from 2300 to 0730 hours. Subjects were in bed during this period. When they awoke at 0730, a test agent was administered according to double-blind technique. Multiple Sleep Latency Tests (MSLT: 20-minute opportunities to fall asleep in bed while EEG and eye movements are recorded) were given at two-hour intervals throughout the day, and a 30-minute vigilance performance test was given at 1000 and 1600 hours. Subjects receiving cetirizine in doses of 5 to 20 mg did not differ from placebo controls in any objective or subjective measure of daytime alertness. Subjects receiving hydroxyzine were significantly more sedated and showed slower reaction times than the placebo control group for at least four hours after treatment. Self-rated feelings of sleepiness, impairment, and fatigue did not differ significantly between groups. This suggests that hydroxyzine subjects may not have been aware of their sleepiness and slower reaction times.