Sustained-release anhydrous theophylline in preventing exercise-induced asthma

A number of drugs have been taken into consideration as to their efficacy in preventing exercise-induced asthma (EIA), which may be a reliable model for the investigation of bronchodilating agents. 15 asthmatic patients (mean age 21.1 ± 10.7), EIA positive (free running test), were selected for a double-blind cross-over study of a sustained-release theophylline preparation against placebo. Patients underwent four subsequent bronchoprovocation tests by means of free running, at a 3-hours' interval, with a prior administration (3 h before the first test) of the drug at the dose of 7-8 mg/kg or the placebo. Lung function was tested (FEV_1.0, FEF₅₀, FEF₂₅, sGaw) after the four induction tests as regards to the plasma concentrations of theophylline. After 6, 9 and 12 h, respectively, from administration of the drug, theophylline plasma levels between 7 and 9 mg/ml were found, which are to be considered more than satisfactory after an acute administration. A continuous protective activity has been noted against the exercise stress, with a significant difference between drug and placebo, for all lung function parameters with the obvious exception of the first one in which a satisfactory level of theophylline absorption was not reached. The finding of this new positive aspect of the drug investigated appears to be extremely interesting, particularly if added to the already well-known therapeutic activity, and to the fact that often other classes of drugs do not show a good correlation of protective action against EIA and prevention of spontaneous asthmatic attacks.