Melatonin and zopiclone as pharmacologic aids to facilitate crew rest

Purpose: In response to mission imperatives, transport aircrews must often sleep at inappropriate circadian times resulting in inadequate sleep. This study was undertaken to determine whether either melatonin or zopiclone cou ld facilitate early circadian sleep, and to assess whether either of these medications would result in a psychomotor performance decrement which would preclude their use in aircrew. Method: Thirteen subjects from DCIEM comple ted a double-blind cross-over protocol. All subjects were assessed for psyc homotor performance during 3 drug conditions (placebo, 10 mg melatonin, and 7.5 mg zopiclone), which were separated by one week. Each of these conditi ons involved 2 nights of sleep, back-to-back, with the first night being a normal circadian control sleep (23:00 h bedtime, arising at 06:45 h), and t he second night being an early circadian drug sleep (drugs at 16:45 h, 17:0 0 h bedtime, arising at 23:45 h). All subjects were tested for psychomotor performance, on both nights of each of the 3 drug conditions, pre- and post -sleep. Further, during the early circadian drug night, all subjects were t ested every hour after arising at 23:45 h (24:00 h until 07:00 h. At the be ginning of each psychomotor test session, subjects were asked for their sub jective levels of sleepiness and fatigue. Results., Relative to placebo (33 9.5 min) the subjects slept more on melatonin (370.2 min, p < 0.01), and zo piclone (373.3 min, p < 0.01). Performance in serial reaction time (SRT) ta sk (p < 0.001), logical reasoning task (LRT) (p < 0.001), serial subtractio n task (SST) (p < 0.02), and Multitask (MT) (p < 0.03) were impaired for al l 3 drug conditions immediately on awakening, compared with pre-sleep perfo rmance, as a result of a sleep-inertia effect. With respect to the subjecti ve data, sleep inertia effects were evident (or sleepiness (p < 0.001), men tal fatigue (p < 0.002), and physical fatigue (p < 0.05). For SRT, LRT, and SST, performance recovered to pre-sleep levels within 1.25 h of awakening, and for MT recovery occurred 2.25 h after awakening. There were no differe nces in performance or subjective measures between placebo, melatonin and z opiclone. Conclusions: Both zopiclone and melatonin improved sleep relative to placebo. After sleep inertia, performance recovered to pre-sleep levels for all tasks and was sustained at that level throughout tile balance of t he testing period. There was no impact of melatonin or zopiclone on perform ance measures compared with placebo.