Eszopiclone: an update on its use in insomnia.

Eszopiclone is the single (S)-enantiomer of the cyclopyrrolone hypnotic zopiclone. It was marketed in the U.S. in December 2004. Its kinetics and possible mode of action, pivotal regulatory trials and its use in insomnia comorbid with other conditions are reviewed, together with trials in patients with obstructive sleep apnea syndromes. Safety and tolerability aspects are discussed, including its dysgeusic profile and effects on memory, cognitive and psychomotor function. U.S.-based pharmacoeconomic data are included together with the design features of key regulatory studies submitted for regulatory approval in Japan.