Single-Dose Cross-Over Study of the Effects of Albuterol-HFA in Exercise Induced Bronchoconstriction

The prevalence of exercise-induced bronchoconstriction (EIB) has been reported to be around 70% to 75% among patients with clinically established asthma. Airway cooling and drying are thought to cause the release of inflammatory mediators, such as histamine and leukotrienes, which then mediate clinical EIB symptoms. Pretreatment with a variety of medications will ameliorate EIB. Albuterol has been found to be more effective in minimizing EIB than theophylline, ipratropiom, cromoglycate, etc. Tested using a treadmill exercise challenge, the newer formulations of albuterol MDI with HFA as propellant have been demonstrated to be as effective as those with CFC as propellant in protecting asthma patients from EIB in children and adults. As a part of the Amphastar Pharmaceuticals' clinical development plan, the current study examines the clinical efficacy of A004, Armstrong Pharmaceuticals' Albuterol HFA oral inhalation MDI, in preventing EIB in adolescent and adult asthmatic patients. This is a randomized, double-blind, active and placebo-controlled, three-treatment, cross-over study, to be conducted in adolescent and adult patients with mild to moderate asthma and demonstrable EIB. All subjects will be screened against the inclusion/exclusion criteria for enrollment. A computer-generated randomization code will be created by the Amphastar Pharmaceuticals' IT Department, so that each enrolled subject will receive all three double-blinded treatments in randomized sequence. Each treatment is followed by a standardized exercise challenge and a series of FEV1 measurements during the 90 min post-exercise period. The three crossover Treatment Arms are: * Treatment T (Armstrong's Test Drug: Albuterol-HFA); * Treatment R (Reference Drug and Active Control: Proventil®-HFA); * Treatment P (Placebo-HFA). By the definition of the crossover design, the three Treatment Arms are expected to consist comparably of 24 evaluable subjects. The consecutive study sessions will be separated by an interval of 1-14 days.