(R,S)-hydroxy Ramelteon metabolite M-II is a mixed isomer preparation of the melatonin receptor agonist ramelteon metabolite M-II, which is a metabolite of ramelteon .1,2 It has an (R,S) configuration at the hydroxy group, where ramelteon metabolite M-II has the (S) configuration at that position.
1.Nishiyama, K., Nishikawa, H., Kato, K., et al.Pharmacological characterization of M-II, the major human metabolite of ramelteonPharmacology93(3-4)197-201(2014) 2.Nishiyama, K., and Hirai, K.In vitro comparison of duration of action of melatonin agonists on melatonin MT1 receptor: Possible link between duration of action and dissociation rate from receptorEur. J. Pharmacol.75742-52(2015)