Zopiclone N-oxide (RP 29753) is a less active metabolite of Zopiclone. Zopiclone N-oxide is also an impurity of Eszopiclone and is formed by the oxidation of Eszopiclone[1][2].
[1]. C Fernandez, et al. Pharmacokinetics of zopiclone and its enantiomers in Caucasian young healthy volunteers. Drug Metab Dispos. Nov-Dec 1993;21(6):1125-8.
[2]. Yu Sha, et al. Synthesis of RP 48497, an impurity of eszopiclone. Molecules. 2008 Aug 22;13(8):1817-21.
















