A synthetic melatonin analogue with hypnotic and circadian rhythm-modulating activities. Ramelteon binds to and activates melatonin receptors 1 and 2 in the suprachiasmatic nucleus (SCN) of the brain, thereby promoting the onset of sleep. Unlike the nonbenzodiazepine sedative hypnotics zolpidem and zaleplon, this agent does not activate GABA receptors and, so, produces no GABA receptor-mediated anxiolytic, myorelaxant, and amnesic effects.