There is supposed not to be a side effect of the sleepiness due to the second-generation antihistamine intake, even during monotonous vigilance experiments such as driving. It is also well known that the manifestation of the sleepiness is strongly influenced in the circasemidian rhythm at the daytime. Therefore, we investigated the effect of epinastine hydrochloride (Alesion® 20mg) on physiological sleepiness during driving simulator operation at this time zone. The subjects were 16 male Japanese cedar pollinosis sufferers. Eight of them were assigned as the morning group (10:00–12:00, 36.1±10.5 yrs) and the rest were assigned as the afternoon group (12:00-15:00, 39.8±8.2 yrs). In the morning group, the drug was administered at 09:00, at 12:00 in the afternoon group. After 60 min from the drug intake, they operated a driving simulator for 120 min (15 min×4 trials×2 sessions). We measured EEG derivation from Pz during operating the simulator and analyzed theta power density (3.0~6.0Hz). And we collected blood samples (8cc) from the non-dominated arm after 60, 120, 180 and 240 min after the drug intake. The results showed that there was a significant difference between both groups in the blood concentration of epinastine hydrochloride after 60 min from the drug intake (p=0.04). Theta power density of the afternoon group at both sessions had significantly higher values than that of the morning group (ss1; p=0.005, ss2; p=0.024). The conclusion was that one should not drive a car, even if second-generation antihistamine had been administrated in the early afternoon.
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