Residual effects of sleep medication on driving ability

Most patients using hypnotics are ambulatory and presumably have a job and drive a car. Since driving a car is one of the most common but potentially dangerous daily activities, hypnotics should act rapidly when needed, but daytime sleepiness and other residual effects that may impair performance are unwanted. This review summarizes the effects of hypnotics on driving ability as determined with the on-the-road driving test during normal traffic. Supportive evidence from epidemiological data, and results from driving simulators and closed-road studies are also considered. On-the-road studies revealed that benzodiazepine hypnotics significantly impaired driving ability the morning following bedtime administration. Impairment was sometimes also significant in the afternoon (16-17 h after administration). Similar driving impairment was observed with zopiclone. However, the magnitude of impairment depends on various factors including the half-life and dosage of the drug, and the time after administration. The results from on-the-road driving studies are supported by evidence obtained in driving simulators and laboratory tests. Epidemiological data and on-the-road studies show that tolerance develops to the impairing effects of hypnotics. However, this is a slow process, and impairment may persist. Patients treated with benzodiazepine hypnotics or zopiclone should be cautioned when driving a car. Both zolpidem and zaleplon do not significantly affect driving performance the morning following bedtime administration. Middle-of-the-night administration of zolpidem significantly impairs driving ability in a dose-dependent manner. In contrast, zaleplon did not affect driving ability 4 h after middle-of-the-night administration.