Effects of tandospirone, a 5-HT1A receptor-related anxiolytic, on daytime sleepiness and psychomotor functions: a comparative double-blind study with diazepam.

A double-blind cross-over placebo-controlled study was designed to compare the effects of a single oral dose of tandospirone (30 mg), a new 5-HT1A receptor-related anxiolytic, on daytime sleepiness, psychomotor function and short-term memory with those of diazepam (5 mg), a benzodiazepine, in 12 healthy Japanese volunteers. A dose of 5 mg of diazepam significantly shortened sleep latencies measured by the Multiple Sleep Latency Test during the periods of 3 to 7 h after the medication, with no influence on the self-estimated sleepiness on the Stanford Sleepiness Scale. The elevated daytime sleepiness under the diazepam treatment was correlated with impaired psychomotor performance; performance on the visual vigilance task significantly declined 1.5 to 3.5 h after the administration of 5 mg of diazepam. In contrast, 30 mg of trandospirone did not impair objective measures of daytime wakefulness or performances. The differential effects of the two anxiolytics on daytime sleepiness and psychomotor functions could be ascribable to the differences in their pharmacological mechanisms of actions. The findings also suggested the superiority of tandospirone to the benzodiazepine in terms of behavioral side effects.