Differential residual effects of zaleplon and zopiclone on actual driving: a comparison with a low dose of alcohol.

Study Objectives: To compare residual effects of zaleplon 10 mg, zopiclone 7.5 mg, and placebo, and a social dose of alcohol on car driving, memory, and psychomotor performance.

Design: Two-part placebo controlled, crossover study. Part 1 was single blind, Part 2 double blind.

Setting: University research institute.

Participants: Thirty healthy volunteers (15 men and 15 women, mean age 32 +/- 7 years)

Interventions: In Part 1 alcohol and alcohol-placebo drinks were administered around noon. In Part 2 single oral doses of zaleplon 10 mg, zopiclone 7.5 mg and placebo were administered at bedtime.

Measurement And Results: A highway driving test, laboratory tests of word learning, critical tracking and divided attention, and subjective assessments of sleep, mood, and effects of treatments on driving. Driving started 40 minutes after a second alcohol dose in Part 1, and 10 hours after drug intake in Part 2. The results demonstrated that alcohol, at average plasma concentrations of approximately 0.030 g/dl, significantly impaired performance in all tests. Zaleplon's residual effects did not differ significantly from those of placebo in any test. In contrast, zopiclone had significant residual effects on driving, divided attention, and memory. The magnitude of impairment in the driving test observed the morning after zopiclone 7.5 mg was twice that observed with alcohol.

Conclusion: Zaleplon 10 mg has no residual effects on driving when taken at bedtime, 10 hours before driving. In contrast, zopiclone 7.5 mg can cause marked residual impairment. Patients should be advised to avoid driving the morning after zopiclone administration.