Effects of zopiclone on the rest/activity rhythm after a westward flight across five time zones

The effects of zopiclone on the rest/activity rhythm were investigated after a westward flight with a 5-h phase delay (Grenoble-Martinique). The rest/activity rhythm was recorded continuously with an actigraph monitor during a 6-day baseline episode in Grenoble and a 6-day sojourn in Martinique. Rectal temperature was recorded before the flight on day 2 and after the flight on days 2 and 5. Subjective jet-lag score was assessed before the flight on days 1 and 2 and in Martinique on days 1, 2, 5 and 6. Zopiclone (7.5 mg) or placebo were administered double blind 30 min prior to bedtime during the first 4 post-flight days (D1-D4). Under zopiclone treatment, sleep was less fragmented on the first post-flight night and the curtailment of sleep duration observed on D2 and D3 under placebo was prevented. During day-time, subjects tended to be more active than with placebo. By contrast, subjective jet-lag scores did not differ between both groups. Zopiclone seemed to accelerate the readjustment of the rest/activity rhythm and the normalisation of the phase relationship between sleep and the temperature rhythm. Zopiclone probably exerts its "resetting" effects on jet-lag desynchronosis by facilitating sleep induction rather than via a chronobiotic action.