Eszopiclone [Lunesta, Estorra] is a short-acting hypnotic agent that is a stereoselective isomer of the agent zopiclone, which has been available in Europe since 1992. Eszopiclone is structurally unrelated to the benzodiazepines, and Sepracor (the originator of eszopiclone) has stated that the drug acts rapidly, with the duration of effect lasting up to 6 hours. This may result in improved sleep maintenance, with less nocturnal awakening

Originally, racemic zopiclone was developed and marketed by Rhoˆne-Poulenc Rorer, which merged with Hoechst Marion Roussel to form Aventis

Sepracor anticipates that eszopiclone will have equivalent efficacy to the racemic version with potential for an improved side effect profile.