Bitolterol mesylate in exercise-induced asthma.

Exercise-induced asthma is a useful model for evaluating the activity and duration of action of pharmacologic agents of asthma. The main objective of this double-blind, crossover study was to determine the effect of the aerosolized beta-adrenergic agent, bitolterol mesylate, on exercise-induced asthma while its efficacy was being compared with isoproterenol and placebo. Twelve subjects with exercise-induced asthma performed cycloergometer exercise 45 minutes after three inhalations of bitolterol mesylate aerosol (1050 micrograms), or isoproterenol (255 micrograms), or placebo in random sequence. Bitolterol mesylate aerosol was very effective in protecting against exercise-induced asthma. The mean percent maximal decrease of FEV1 after exercise was 5.0% for bitolterol, 22.2% for isoproterenol, and 23.2% for placebo. Subjects experienced skeletal muscle tremor with both bitolterol mesylate (four subjects) and isoproterenol (three subjects), but not with placebo. No other side effects were noted.