Investigation of the usefulness of zaleplon at two doses to induce afternoon-sleep under noise interference and its effects on psychomotor performance and vestibular function

BACKGROUND: Military operation personnel often suffer from sleep difficulty because of their work requirements. In this study, we investigated the efficacy of zaleplon at two doses to induce afternoon-sleep under noise interference and its effects on psychomotor performance and vestibular function; we subsequently established the optimal dosage regimen for military operation personnel. METHODS: Twenty-two healthy young male volunteers were recruited for the study. Eight subjects took 10 mg or 15 mg of zaleplon and placebo alternately and then were exposed to noise. Changes in polysomnography (PSG) indices, including sleep latency (SL), sleep efficiency (SE) and sleep structure, were recorded after drug administration. After awakening, the volunteers’ subjective judgments of sleep quality and sleepiness were measured. Eight volunteers underwent 3 psychomotor performance tests at a one-week interval, and the psychomotor performance tests were conducted before and after taking zaleplon and placebo. Six volunteers participated in the vestibular function test session, and parameters, including optokinetic nystagmus (OKN), vestibular ocular reflex (VOR), visual-vestibular ocular reflex (VVOR) and vestibular ocular reflex fixation suppression (VOR-Fix), were detected by the same experimental design as described above. The data of sleep observations were subjected to one-way variance analysis. RESULTS: Compared with the placebo group, SL was shortened significantly, and the scores of subjective sleep quality and sleep depth were clearly increased in the zaleplon 10 mg group (P < 0.05). Moreover, the SE and the percent of REM (rapid eye movement) sleep were increased remarkably in the zaleplon 15 mg group (P < 0.01). Furthermore, the SE, percent of REM sleep and scores of subjective sleep depth in the zaleplon 15 mg group were significantly higher than in the zaleplon 10 mg group (P < 0.05). The psychomotor performance did not change significantly after ingestion of 10 mg or 15 mg of zaleplon, whereas the OKN and VOR gains were lower in the two dose groups of zaleplon (P < 0.05) and restored to normal 3 h after drug ingestion. CONCLUSION: Zaleplon is an ideal hypnotic for military personnel, and its hypnotic efficiency is dose-related under noise interference; a 15 mg dose of zaleplon could provide significantly better sleep than a 10 mg dose of zaleplon.