The excretion of zopiclone into breast milk.

1. The excretion of zopiclone into breast milk was studied in 12 lactating women in the early postpartum period following the oral administration of a single zopiclone tablet (7.5 mg). 2. The milk/plasma AUC ratio of zopiclone was 0.51 +/- 0.09 (mean +/- s.d.). Individual mean milk/plasma concentration ratios of zopiclone showed significant interindividual variation (range 0.41-0.70). 3. A comparison of pharmacokinetic parameters in the postpartum women with those reported previously in non-pregnant women, showed significantly higher Cmax values in the lactating mothers; tmax occurred later in milk than in maternal plasma. 4. Assuming a daily milk intake of 0.15 l kg-1 and 100% absorption the average infant dose of zopiclone in milk would be 1.4% of the weight adjusted dose ingested by the mother.