Central effects of cinnarizine: restricted use in aircrew.

Hypothesis: Our aim was to establish the effects of cinnarizine, a drug used for the treatment of motion sickness, on daytime sleepiness and performance. Methods: The effects of cinnarizine (15, 30, and 45 mg) were assessed on digit symbol substitution, tracking, vigilance, and on subjective and objective (daytime sleep latencies) sleepiness in six healthy volunteers between the ages of 20 and 34 yr (mean 27 yr) from 1.0 h prior to ingestion to 8.0 h after ingestion. The study was placebo-controlled and double-blind in a six-way, cross-over design. Promethazine (10 mg) was used as an active control. Results: No effects of 15 mg cinnarizine were observed on performance. Sleep latencies were reduced at 3.5 and 5.0 h after ingestion, and the subjects as a group reported increased sleepiness at 5.0 and 6.5 h after ingestion. With 30 mg cinnarizine there was evidence of impaired performance at 5.0, 6.5, and 8.0 h after ingestion. Sleep latencies were not reduced, but the subjects as a group reported increased sleepiness 5.0 h after ingestion. With 45 mg cinnarizine there was evidence of impaired performance 5.0 h after ingestion. Sleep latencies were reduced at 5.0 and 6.5 h after ingestion, and the subjects as a group reported increased sleepiness 6.5 h after ingestion. Promethazine (10 mg) shortened sleep latencies from 2.5 to 5.0 h after ingestion, and the subjects as a group reported increased sleepiness over this period. Conclusion: Cinnarizine is not free of central activity over the usual therapeutic dose range of 15 to 30 mg. It is contraindicated for motion sickness in aircrew involved in the control of aircraft. Caution should be exercised in the use of the drug by other aircrew who may be involved in tasks which demand continued attention.