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 afte r a westward flight with a 5-h phase delay (Grenoble -Martinique). The resu lt/activity rhythm was recorded continuously with an actigraph monitor duri ng 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 fl ight on days 2 and 5. Subjective jet-lag score was assessed before the flig ht 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 durin g the first 4 post-flight days (D1-D4). Under zopiclone treatment, sleep wa s less fragmented on the first post-flight night and the curtailment of sle ep duration observed on D2 and D3 under placebo was prevented. During dayti me, subjects tended to be more active than with placebo. By contrast, subje ctive jet-lag scores did not differ between both groups. Zopiclone seemed t o accelerate the readjustment of the rest/activity rhythm and the normalisa tion of the phase relationship between sleep and the temperature rhythm. Zo piclone probably exerts its "re-setting" effects on jet-lag desynchronosis by facilitating sleep induction rather than via a chronobiotic action.