ATC Group: N05CH Melatonin receptor agonists

Melatonin is a naturally occurring hormone produced by the pineal gland and is structurally related to serotonin. Physiologically, melatonin secretion increases soon after the onset of darkness, peaks at 2-4 am and diminishes during the second half of the night. Melatonin is associated with the control of circadian rhythms and entrainment to the light-dark cycle. It is also associated with a hypnotic effect and increased propensity for sleep.

Ramelteon is a melatonin receptor agonist with both high affinity for melatonin MT₁ and MT₂ receptors and relative selectivity over the MT₃ receptor. The activity of ramelteon at the MT₁ and MT₂receptors is believed to contribute to its sleep-promoting properties, as these receptors, acted upon by endogenous melatonin, are thought to be involved in the maintenance of the circadian rhythm underlying the normal sleep-wake cycle.

Tasimelteon is a circadian regulator that resets the master body clock in the suprachiasmatic nucleus (SCN). Tasimelteon acts as a Dual Melatonin Receptor Agonist (DMRA) with selective agonist activity at the MT₁ and MT₂ receptors. These receptors are thought to be involved in the control of circadian rhythms.