Background: The purpose of this study was to compare the protection afforded by individualized doses of theophylline and a cromolyn metered-dose inhaler (MDI) during allergen challenge.
Methods: The study design was randomized, double-blind, and crossover. Responses to inhaled allergen were measured in 16 subjects with allergic asthma (age range, 18 to 35 years) after 7 days of treatment with either placebo, once daily slow-release theophylline producing a mean +/- SD serum concentration of 16 +/- 5 micrograms/ml during the late phase, or 2 mg of cromolyn administered by MDI four times daily. Forced expiratory volume in 1 second was measured at frequent intervals, and airway responsiveness to histamine was measured before and 3 hours after allergen challenge.
Results: The mean +/- SD maximum decrease in forced expiratory volume in 1 second during the late phase was 30% +/- 14% during placebo treatment, 16% +/- 13% during theophylline treatment, and 13% +/- 14% during cromolyn treatment (placebo vs theophylline and cromolyn, p = 0.0001; theophylline vs cromolyn, p = 0.1). The geometric mean fold increase in airway responsiveness was 3.0 +/- 1.7 during placebo treatment, 1.7 +/- 1.7 during theophylline treatment, and 1.5 +/- 1.6 during cromolyn treatment (placebo vs theophylline and cromolyn, p = 0.0001; theophylline vs cromolyn, p = 0.1).
Conclusions: Theophylline, when administered once daily as a slow-release formulation, was as effective as cromolyn, administered four times daily through an MDI, in attenuating airway responses to inhaled allergen. The protection afforded by both treatments, however, was modest when compared with the results of similar studies with inhaled corticosteroids or other cromolyn formulations that deliver more drug to the lungs than the MDI available in the United States.