Eszopiclone
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Eszopiclone
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| Systematic (IUPAC) name | |
| [(9S)-8-(5-chloropyridin-2-yl)-7-oxo-2,5,8- triazabicyclo[4.3.0]nona-1,3,5-trien-9-yl] 4-methylpiperazine-1-carboxylate |
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| Identifiers | |
| CAS number | 138729-47-2 |
| ATC code | N05CF01 |
| PubChem | 969472 |
| DrugBank | APRD00431 |
| Chemical data | |
| Formula | C17H17N6ClO3 |
| Mol. weight | 388.808 g/mol |
| Pharmacokinetic data | |
| Bioavailability | ? |
| Protein binding | 52-59% |
| Metabolism | Hepatic oxidation and demethylation (CYP3A4 and CYP2E1-mediated) |
| Half life | 6 hours |
| Excretion | Renal |
| Therapeutic considerations | |
| Pregnancy cat. |
C (U.S.) |
| Legal status |
Schedule IV (U.S.) |
| Routes | Oral |
Eszopiclone, available under the brand-name Lunesta, is a nonbenzodiazepine hypnotic agent, is a cyclopyrrone, which is used as a medication in treatment of insomnia. Eszopiclone is the active stereoisomer of zopiclone. Eszopiclone is a white to light-yellow crystalline solid. It is very lightly soluble in water, slightly soluble in ethanol and soluble in aqueous phosphate buffer (pH 3.2).
The precise mechanism of action of eszopiclone as a hypnotic is unknown, but its effect is believed to result from its interaction with GABA receptor complexes at bindings domains located close to or allosterically coupled to benzodiazepine receptors.
Lunesta, which was developed by Sepracor, is FDA approved for long-term use; trials suggest that patients do not get addicted to Lunesta.
Side effects of eszopiclone may include unpleasant taste, headache, drowsiness and dizziness. Those who experience the unpleasant taste experience it upon awakening and describe it as metallic. Some experience the mild-to-moderate taste up to 24 hours after taking the drug, which should go away by performing morning rituals (i.e., brushing teeth, using mouthwash). Some doctors suggest drinking something acidic, such as orange juice, to remedy this side effect.
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[edit] Pharmacodynamics
The precise mechanism of action of eszopiclone as a hypnotic is unknown, but its effect is believed to result from its interaction with GABA-receptor complexes at binding domains located close to or allosterically coupled to benzodiazepine receptors. Eszopiclone is a nonbenzodiazepine hypnotic that is a pyrrolopyrazine derivative of the cyclopyrrolone class with a chemical structure unrelated to pyrazolopyrimidines, imidazopyridines, benzodiazepines, barbiturates, or other drugs with known hypnotic properties.
[edit] Pharmacokinetics
The pharmacokinetics of eszopiclone have been investigated in healthy subjects (adult and elderly) and in patients with hepatic disease or renal disease. In healthy subjects, the pharmacokinetic profile was examined after single doses of up to 7.5 mg and after once-daily administration of 1, 3, and 6 mg for 7 days. Eszopiclone is rapidly absorbed, with a time to peak concentration (tmax) of approximately 1 hour and a terminal-phase elimination half-life (t½) of approximately 6 hours. In healthy adults, Lunesta does not accumulate with once-daily administration, and its exposure is dose-proportional over the range of 1 to 6 mg. In patients 65 years of age and older, there is a slight prolonged elimination of eszopiclone (t½ of approximately 9 hours). Therefore, in elderly patients the starting dose of Lunesta should be decreased to 1 mg and the dose should not exceed 2 mg.
[edit] Absorption
Eszopiclone is rapidly absorbed following oral administration. Peak plasma concentrations are achieved within approximately 1 hour after oral administration. Eszopiclone is weakly bound to plasma protein (52-59%). The large free fraction suggests that eszopiclone disposition should not be affected by drug-drug interactions caused by protein binding. The blood-to-plasma ratio for eszopiclone is less than one, indicating no selective uptake by red blood cells.
[edit] Metabolism
Following oral administration, eszopiclone is extensively metabolized by oxidation and demethylation. The primary plasma metabolites are (S)-zopiclone-N-oxide and (S)-N-desmethyl zopiclone; the latter compound binds to GABA receptors with substantially lower potency than eszopiclone, and the former compound shows no significant binding to this receptor. In vitro studies have shown that CYP3A4 and CYP2E1 enzymes are involved in the metabolism of eszopiclone. Eszopiclone did not show any inhibitory potential on CYP450 1A2, 2A6, 2C9, 2C19, 2D6, 2E1, and 3A4 in cryopreserved human hepatocytes.
After oral administration, eszopiclone is eliminated with a mean t½ of approximately 6 hours. Up to 75% of an oral dose of racemic zopiclone is excreted in the urine, primarily as metabolites. A similar excretion profile would be expected for eszopiclone, the S-isomer of racemic zopiclone. Less than 10% of the orally administered eszopiclone dose is excreted in the urine as parent drug.
In healthy adults, administration of a 3 mg dose of eszopiclone after a high-fat meal resulted in no change in AUC, a reduction in mean Cmax of 21%, and delayed tmax by approximately 1 hour. The half-life remained unchanged, approximately 6 hours. The effects of Lunesta on sleep onset may be reduced if it is taken with or immediately after a high-fat/heavy meal.
