A nonbenzodiazepine cyclopyrrolone and active dextrorotatory stereoisomer of zopiclone with hypnotic and sedative activities and without significant anxiolytic activity. Although the exact mechanism of action remains to be fully elucidated, eszopiclone binds to and activates the omega-1 subtype of the alpha subunit of the gamma-aminobutyric acid-benzodiazepine GABA receptor complex (GABA-A), a chloride ionophore complex in the central nervous system (CNS). This leads to the opening of chloride channels, causing hyperpolarization and inhibition of neuronal firing, which may result in a hypnotic effect and the induction of sleep.