Molecule

Drug Groups

approved; investigational

Description

Ramelteon is the first in a new class of sleep agents that selectively binds to the melatonin receptors in the suprachiasmatic nucleus (SCN). It is used for insomnia, particularly delayed sleep onset. Ramelteon has not been shown to produce dependence and has shown no potential for abuse.

Indication

For the treatment of insomnia characterized by difficulty with sleep onset.

Pharmacology

Ramelteon is the first selective melatonin agonist. It works by mimicking melatonin (MT), a naturally occuring hormone that is produced during the sleep period and thought to be responsible for the regulation of circadian rhythm underlying the normal sleep-wake cycle. Ramelteon has a high affinity for the MT₁ and MT₂ receptors. The MT₁ and MT₂ receptors are located in the brain's suprachiasmatic nuclei (SCN),which is known as the body's "master clock" because it regulates the 24-hour sleep-wake cycle. Ramelteon has an active metabolite that is less potent but circulates in higher concentrations than the parent compound. The metabolite also has weak affinity for the 5HT2b receptor.

Affected Organisms

Biotransformation

Hepatic

Absorption

Rapid, total absorption is at least 84%.

Half Life

~1-2.6 hours

Protein Binding

~82% (in human serum)

Elimination

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.

Distribution

* 73.6 L

References

External Links