Efficacy and Safety of Levalbuterol Versus Racemic Albuterol in Asthma

Inclusion Criteria: * Male and female subjects must be at least greater than or equal to 18 years of age at the time of consent. * Subjects must have history of asthma for at least 6 months. * Subjects must present to the emergency department (ED) or clinic with forced expiratory volume in one second (FEV1) of 20 to 55% (inclusive) predicted at baseline * Subjects must have O2 saturation greater than or equal to 90% at room air or with no more than 6 Liters/minute supplemental oxygen and no other cause of wheezing or shortness of breath other than asthma as determined by the physician. * Prior use of a beta-agonist (e.g., Primatine Mist, albuterol, salmeterol, etc.) within 24 hours of presentation to the ED or Clinic. * Smoked ≤ 10 pack-years or non-smoker. * Be in good health with the exception of asthma and not suffering from any chronic condition which might affect their lung function, such as COPD or emphysema. * Near-normal activity level between exacerbations. * Subjects who are taking inhaled or systemic corticosteroids must be on a stable dose for at least 21 days prior to study entry. Exclusion Criteria: * Subjects who have received treatment for asthma in an ED, Clinic, or Urgent Care Center within 2 weeks prior to study entry. * Based upon history or physical exam in the ED or Clinic, subjects with known or suspected cause of pulmonary symptoms other than asthma, such as COPD, CHF, pneumonia, pulmonary embolism, or angioedema. * Subjects with a history of asthma episodes associated with hypercapnia, respiratory arrest, hypoxic seizures, or requiring intubation within 12 months prior to entry. * Hospitalization for asthma within two months prior to entry. * Female subjects who are pregnant or lactating. * Subjects who have a history of a clinically significant psychiatric disorder within the last 3 months, with the exception of mild depression. * Subjects who have participated in an investigational drug study within 30 days of study entry or have previously participated in the current trial.