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Ramelteon
- indication:For the treatment of insomnia characterized by difficulty with sleep onset.
- pharmacologypharmacology:
- mechanism: Ramelteon is a melatonin receptor agonist with both high affinity for melatonin MT<sub>1</sub> and MT<sub>2</sub> receptors, and lower selectivity for the MT<sub>3</sub> receptor. Melatonin production is concurrent with nocturnal sleep, meaning that an increase in melatonin levels is related to the onset of self-reported sleepiness and an increase in sleep propensity. MT<sub>1</sub> receptors are believed to be responsible for regulation of sleepiness and facilitation of sleep onset, and MT<sub>2</sub> receptors are believed to mediate phase-shifting effects of melatonin on the circadian rhythm. While MT<sub>1</sub> and MT<sub>2</sub> receptors are associated with the sleep-wake cycle, MT<sub>3</sub> has a completely different profile, and therefore is not likely to be involved in the sleep-wake cycle. Remelteon has no appreciable affinity for the gamma-aminobutyric acid (GABA) receptor complex or receptors that bind neuropeptides, cytokines, serotonin, dopamine, norepinephrine, acetylcholine, or opiates.
- toxicity:
- absorprion: Rapid, total absorption is at least 84%.
- halflife: ~1-2.6 hours
- roouteelimination: Following oral administration of radiolabeled ramelteon, 84% of total radioactivity was excreted in urine and approximately 4% in feces, resulting in a mean recovery of 88%. Less than 0.1% of the dose was excreted in urine and feces as the parent compound.
- volumedistribution: * 73.6 L
- clearance: