Pharmacokinetic and clinical parameters of zopiclone and trimipramine when administered simultaneously to volunteers

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Abstract
Zopiclone is a new sedative showing a rapid onset of hypnotic effect and a relatively short duration of action. The goal of this study was to assess the kinetic parameters of zopiclone and its interaction with trimipramine when administered concomitantly. Ten normal subjects each received doses of zopiclone (7·5 mg), trimipramine (50 mg), and zopiclone (7·5 mg) + trimipramine (50 mg) orally at 7‐day intervals. The absorption of zopiclone was rapid, the observed plasma peak concentration and 95 per cent of all absorption occurring within one hour. The average elimination half‐life was 3·8 ± 0·2 h. The volunteers reported a bitter taste at an average of 24 min after zopiclone administration at which time concentrations in saliva were approximately 50 ng ml−1. Trimipramine decreased the relative bioavailability determined for zopiclone by 13·7 per cent, while zopiclone decreased the relative bioavailability of trimipramine by an average of 26·6 per cent, although neither of these changes was statistically significant (p > 0·05); there were no substantial changes in other kinetic parameters. It is concluded that zopiclone presents advantages over some other sedative drugs as it is rapidly absorbed and eliminated. When zopiclone is administered with trimipramine, the decrease in the relative bioavailability of trimipramine may be clinically significant.