Theophylline mitigates the bronchoconstrictor effects of sulfur dioxide in subjects with asthma.

The objective of the study was to investigate the ability of a sustained-release (SR) theophylline tablet (Uniphyl; Purdue Frederick Co., Norwalk, Conn.) to block or mitigate sulfur dioxide (SO2)-induced bronchoconstriction in adult subjects with asthma. Eight subjects participated in a double-blind, crossover study with a 400 mg theophylline tablet or placebo once a day for a week before a 10-minute SO2 challenge. FEV1 and total respiratory resistance (RT) were measured before and after the SO2 challenge and on a different day before and after an air exposure. After exposure to SO2, average values of FEV1 dropped 16% after placebo treatment and 7% after theophylline treatment. The corresponding percentages for RT were a 37% increase after placebo and a 7% increase after theophylline treatment. Analysis of variance demonstrated a significant difference between the SO2-induced decrease in FEV1 and increase in RT after SR theophylline treatment compared with that of placebo treatment. Thus, we conclude that SR theophylline tablets, taken at this concentration for 1 week, mitigate SO2-induced bronchoconstriction.