The primary objective of this study is to investigate the efficacy of levalbuterol 90 ug (2 actuations, 45 ug each) versus placebo (2 actuations) in the treatment and prevention of bronchoconstriction in adolescent and adult subjects with asthma, with all treatments administered 4 times a day (QID).

A double-blind, randomized, placebo- and active-controlled, multicenter, parallel-group trial of levalbuterol in subjects 12 years of age and older with asthma. Study participation will include one 1-week single-blind placebo run-in and an 8-week, randomized,double-blind, active-treatment period with four treatment groups. This study was previously posted by Sepracor Inc. In October 2009, Sepracor Inc. was acquired by Dainippon Sumitomo Pharma., and in October 2010, Sepracor Inc's name was changed to Sunovion Pharmaceuticals Inc.

Inclusion Criteria

• Must give written informed consent (IC) prior to participation in the study. For subjects 12 - 17 years of age, the IC must be signed parent or legal guardian. Females must sign the Women of Childbearing Potential Addendum
• Be willing and able to comply with the study procedures and visit schedules
• Male or female, at least 12 years of age
• Females 12-60 years of age must have a negative serum pregnancy test at Visit 1 (V1)
• Women of child bearing potential must be using an acceptable method of birth control
• Must have a documented diagnosis of asthma for a min. of 6 mos. prior to V1
• At V1, the subject must demonstrate a baseline FEV1 within >45% and <75% of predicted for their height, age, gender, and race
• Following abstention from medications used to treat asthma, subject must demonstrate >12% reversibility of airflow obstruction within 15-30 min. following inhalation of 180 µg (2 actuations, 90 µg ea.) of racemic albuterol MDI
• Must have stable baseline asthma and have been using a B-adrenergic agonist, and/or anti-asthma anti-inflammatory medication, and/or OTC asthma medication for at least 6 mos. prior to V1
• Must be in good health with the exception of their reversible airways disease and not suffering from any chronic condition that might affect their respiratory function
• Must have a chest X-ray that is not diagnostic of pneumonia, atelectasis, pulmonary fibrotic disease, pneumothorax, chronic obstructive pulmonary disease, etc.
• Must be able to complete the diary cards and medical event calendars reliably on a daily basis and demonstrate how to use the MiniWright PEF meter

Exclusion Criteria

• Subject who is expected to require any disallowed medications
• Female subject who is pregnant or lactating
• Subject who has participated in an investigational drug study within 30 days prior to V1, or who is currently participating in another clinical trial
• Schedule prevents him or her from taking the first daily dose of study medication and/or starting study visits before 9AM
• Subject who has travel commitments during the study that would interfere with trial measurements or compliance or both
• Subject who has a history of hospitalization for asthma within 45 days prior to V1, or who is scheduled for in-patient hospitalization during the trial
• Have a known sensitivity to levalbuterol or racemic albuterol, or any of the excipients contained in any of these formulations
• Subject using any prescription drug with which albuterol sulfate administration is contraindicated
• Subject with currently diagnosed life-threatening asthma
• Subject with clinically significant abnormalities that may interfere with the metabolism or excretion of the study drug
• Have a history of cancer (exception: basal cell carcinoma in remission)
• Have hyperthyroidism, diabetes, hypertension, cardiac diseases, or seizure disorders not well controlled by medication or that may interfere with the successful completion of this protocol
• Have a history of substance or drug abuse within 12 mos. preceding V1 or a positive urine drug screening at V1
• Have greater than 10 pack year history of cigarette smoking or use of any tobacco products within 6 mos. of V1
• Have a documented history of bronchopulmonary aspergillosis or any form of allergic alveolitis
• Have suffered from a clinically significant upper or lower respiratory tract infection in the 2 weeks prior to V1
• Have any clinically significant abnormal laboratory values
• Have a clinically significant abnormal 12-lead ECG that may jeopardize the subject's ability to complete study
• Subject who is a staff member or relative of a staff member