Lunesta (eszopiclone) is a nonbenzodiazepine hypnotic agent. (The leading prescription insomnia drugs, including Ambien and Sonata are also nonbenzodiazepine agents.) It should be used only when the recipient can devote a full night's sleep because it will take that long to wear off. One rap against zolpidem (Ambien) was that while it helps people get to sleep, they wake up during the night. Eszopiclone may be better in that respect. Also, while Ambien is officially supposed to be taken for only 10 days straight (although some doctors ignored that limit), Eszopiclone/Lunesta is approved for longer durations. People don't tend to get addicted to Lunesta.
The pharmacology of eszopiclone is not well understood. Chemically, eszopiclone is a short-acting hypnotic agent that is a stereoselective isomer of the agent zopiclone. Racemic zopiclone (both forms of the isomer) has been on the market in Europe since 1992. It is not widely used in the United States.
Formerly known as Estorra, Lunesta is sold in 1 mg, 2 mg and 3 mg tablets. The recommended dosing to improve sleep onset and/or maintenance is 2mg or 3mg for adult patients (aged 18-64 years) and 2mg for older adult patients (over 65). The 1 mg dose is for sleep onset in older adult patients whose primary complaint is difficulty falling asleep.
Eszopiclone is actually a sub-set of zopiclone. Zopiclone, like many drugs, is a racematic mizture of two enantiomers. The S nantiomer is the biologically active form. The patent on zopiclone has expired, but the government has apparently granted a patent to just the S-form and therefore considers it a different entity. The benefit of using only one enantiomer is that the dosage can be lower and the inactive enantiomer is not around to cause side effects.
Sepracor, the maker of Estorra™ (eszopiclone) reports:
The Prescription Drug User Fee Act (PDUFA) date for the resubmitted Estorra™ brand eszopiclone New Drug Application (NDA) is December 15, 2004. A PDUFA date is the date by which the U.S. Food and Drug Administration (FDA) is expected to review and act on an NDA submission. On February 27, 2004, Sepracor received an "approvable" letter from the FDA for its NDA for Estorra™ for the treatment of insomnia characterized by difficulty falling asleep and/or difficulty maintaining sleep during the night and early morning. Contingent upon approval from the FDA of the Estorra™ NDA, Sepracor would expect the recommended dosing to achieve sleep onset and maintenance to be 2 mg and 3 mg for adult patients, 2 mg for elderly patients with sleep maintenance difficulties, and 1 mg for sleep onset in elderly patients whose primary complaint is difficulty falling asleep. The FDA has not requested additional clinincal or preclinical trials for approval.