Zopiclone is a new hypnotic cyclopyrrolone with a short elimination half-life (5.3 h). The pharmacokinetic profile of this drug was studied in 7 chronic renal failure (CRF) patients given 7.5 mg nocte for 7 consecutive nights. The pharmacokinetic values obtained were compared with the corresponding values found in healthy young volunteers given the same repeated dosage regimen. C max and T max were not significantly different between the two groups but the C min of unchanged zopiclone (at 24 h) post-dosing was significantly (p less than 0.001) higher in CRF patients (8.16 +/- 5.34 ng/ml) than in healthy volunteers (1.90 +/- 0.82 ng/ml). The AUC values in CRF patients were also significantly increased during the seventh day (742 +/- 212 h ng/ml) compared to healthy subjects (408 +/- 66.5 h ng/ml) and the elimination half-life of zopiclone was also longer in CRF patients (about 8 h) than in the reference group (about 5 h). Nevertheless, the accumulation ratios remained similar in the two groups (1.09 +/- 0.18 in CRF patients and 1.02 +/- 0.2 in healthy subjects). Thus no evident accumulation of zopiclone appeared in the CRF patients. As in the healthy subjects, no metabolites were detected in the plasma of the CRF patients although at steady state the urinary excretion of zopiclone and its N-oxide and N-desmethyl derivatives (2.03% +/- 1.52% and 1.99 +/- 0.65% of the dose, respectively) was significantly decreased compared to healthy subjects (3.7% +/- 2.1% and 32.6% +/- 4.5%, respectively). Zopiclone thus represents a safe alternative to benzodiazepine hypnotic therapy in patients with renal impairment.