LUNESTA(TM) Perimenopause-Menopause Study Data to Be Presented at North American Menopause Society Annual Meeting

Sepracor Inc. (Nasdaq: SEPR) today announces the presentation of results from its Phase IIIB/IV study evaluating safety and efficacy of LUNESTA(TM) brand eszopiclone for treatment of insomnia in perimenopausal and menopausal women at the North American Menopause Society’s annual meeting in San Diego.

In this six-week, 410-patient, randomized, double-blind, placebo-controlled study, nightly use of LUNESTA 3 mg resulted in statistically significant improvement from baseline compared with placebo in patient-reported measures of sleep latency (time to sleep onset; p < or = 0.001), wake time after sleep onset (WASO; a sleep maintenance measurement of the amount of time spent awake after initially falling asleep; p < or = 0.002), and total sleep time (p < or = 0.004) for each week of the four-week, double-blind treatment period. Patients treated with LUNESTA also demonstrated significant improvements in additional sleep measures and measures of daytime function (p < or = 0.05), including sleep quality, sleep depth, daytime alertness, ability to function, ability to think and concentrate clearly, and sense of well-being, versus those patients administered placebo. LUNESTA was well tolerated over the treatment period.

Compared to baseline and averaged over the double-blind period, women treated with LUNESTA reported fewer total nocturnal awakenings (p<0.0001) and fewer awakenings due to hot flashes (p=0.001) compared to those patients administered placebo. A physician global assessment, which is a measure by which physicians evaluate their patients' overall change in menopausal symptoms, was statistically significantly improved (p<0.001) at the end of the treatment period for women treated with LUNESTA 3 mg compared to those treated with placebo. Other findings include improvements from baseline in perimenopausal symptoms as measured by the Greene Climacteric Scale (total score p=0.03; psychological domain p=0.009; and vasomotor p=0.03), by the Menopause Quality of Life Scale (vasomotor p=0.003 and physical p=0.04 domains) and by the Montgomery Aspberg Depression Rating Scale (MADRS; p=0.02).

The study also assessed changes in total sleep time, sleep latency and sleep maintenance in the seven days following patients’ discontinuation of LUNESTA treatment. The LUNESTA treatment group did not experience rebound insomnia after discontinuation of LUNESTA. Rebound insomnia is defined as a dose-dependent temporary worsening of sleep relative to baseline following abrupt discontinuation of treatment.

“One of the effects associated with perimenopause and menopause is increased incidence of waking up during the night and an inability to fall back to sleep, principally due to hot flashes,” said Claudio N. Soares, M.D., Ph.D., Associate Professor, Department of Psychiatry and Behavioral Neurosciences, McMaster University and Co-Director, Women’s Health Concerns Clinic at St. Joseph’s Healthcare, Hamilton, Canada. “This study of LUNESTA in women experiencing perimenopausal and menopausal symptoms suggests that LUNESTA may provide them with relief from insomnia and therefore could potentially lead to a significant improvement in their quality of life.”

“Seventy-five percent of women report symptoms during menopause that can include hot flashes, night sweats and insomnia,” said Karen L. Giblin, President and Founder of PrimePlus/RedHotMamas, a leading menopause education provider. “It is encouraging to see additional research directed toward assessing how LUNESTA might be able to ameliorate the insomnia symptoms that accompany this life change.”

Perimenopause in women is the transition period from regular reproductive function to complete cessation of the menstrual period, or menopause. During this transition, which can be years in duration, and continuing through to the post-menopausal period, the body experiences both physical and hormonal changes, which can be associated with a variety of symptoms. Problems sleeping and resulting fatigue may occur due to waking up in the middle of the night because of hot flashes or a need to go to the bathroom, which can lead to trouble falling back to sleep. During this time, women may also experience trouble falling to sleep or waking up early in the morning. According to the Agency for Healthcare Research and Quality, up to 60 percent of perimenopausal, menopausal, and postmenopausal women experience sleep disturbances.

“We recognize that a significant number of women experience insomnia that co-exists with the physical and hormonal changes and accompanying symptoms that characterize this reproductive transitional period,” said Donna R. Grogan, M.D., Senior Vice President, Clinical Research at Sepracor. “This study, which is part of our Phase IIIB/IV LUNESTA program designed to investigate the effects of LUNESTA on insomnia associated with underlying medical conditions, demonstrated the efficacy and safety of LUNESTA in women with insomnia associated with the menopausal period and explored the added benefit it may provide in alleviating certain perimenopausal/menopausal symptoms.”

LUNESTA is a new non-benzodiazepine indicated for the treatment of insomnia in patients who experience difficulty falling asleep as well as for the treatment of patients who have difficulty sleeping through the night (sleep maintenance difficulty). LUNESTA is approved for long-term use. LUNESTA 1 mg, 2 mg and 3 mg tablets are available by prescription in pharmacies nationwide.

An estimated 100 million adult Americans suffer from either chronic or occasional insomnia.(1) Symptoms of insomnia include difficulty falling asleep, awakening frequently during the night, waking up too early, an inability to fall back to sleep or awakening feeling unrefreshed.

The U.S. market for prescription sleep products was approximately $2.1 billion in 2004, excluding products not indicated for the treatment of insomnia that are nonetheless used in its treatment. This represents nearly a 19 percent increase over the previous year, according to IMS Health information.

Important Safety Information

LUNESTA works quickly and should only be taken immediately before bedtime. Be sure you have at least eight hours to devote to sleep before becoming active. You should not engage in any activity after taking LUNESTA that requires complete alertness, such as driving a car or operating machinery. You should use extreme care when engaging in these activities the morning after taking LUNESTA. Do not use alcohol while taking any sleep medicine. All sleep medicines carry some risk of dependency. Do not use sleep medicines for extended periods without first talking to your doctor. Side effects may include unpleasant taste, headache, drowsiness and dizziness.

Please visit www.sepracor.com or www.lunesta.com to access the FDA-approved labeling text for LUNESTA.

About Sepracor

Sepracor Inc. is a research-based pharmaceutical company dedicated to treating and preventing human disease through the discovery, development and commercialization of innovative pharmaceutical products that are directed toward serving unmet medical needs. Sepracor’s drug development program has yielded an extensive portfolio of pharmaceutical compound candidates with a focus on respiratory and central nervous system disorders. The company’s commercialization efforts are carried out by its U.S.-based, 1,250-person, primary care and specialty-oriented sales force. Sepracor’s corporate headquarters are located in Marlborough, Massachusetts.

This news release contains forward-looking statements that involve risks and uncertainties, including statements with respect to the safety, efficacy and potential benefits of LUNESTA. Among the factors that could cause actual results to differ materially from those indicated by such forward-looking statements are: Sepracor’s ability to fund, and the results of, further clinical trials; the timing and success of submission, acceptance and approval of additional regulatory filings; label/use changes or concerns of LUNESTA prescribers or patients; and certain other factors that are detailed in the company’s quarterly report on Form 10-Q for the quarter ended June 30, 2005 filed with the Securities and Exchange Commission.

In addition, the statements in this press release represent Sepracor’s expectations and beliefs as of the date of this press release. Sepracor anticipates that subsequent events and developments may cause these expectations and beliefs to change. However, while Sepracor may elect to update these forward-looking statements at some point in the future, it specifically disclaims any obligation to do so. These forward-looking statements should not be relied upon as representing Sepracor’s expectations or beliefs as of any date subsequent to the date of this press release.

LUNESTA is a trademark of Sepracor Inc.

1) Extrapolated to current population from 2000 census based on Ancoli-Israel et al. SLEEP. 1999;22 (suppl 2):S347-S353.

For a copy of this release or any recent release, visit www.sepracor.com.