REDUCED PROTECTION AGAINST EXERCISE-INDUCED BRONCHOCONSTRICTION AFTER CHRONIC DOSING WITH SALMETEROL

The purpose of the present study was to assess the degree of protection of inhaled salmeterol against exercise-induced bronchoconstriction (EIB) after chronic compared with single dosing in patients with asthma. Twelve patients with exercise-induced asthma took part in a randomized double-blind crossover study to compare the duration of action of inhaled salmeterol 50 μg twice daily for 4 weeks with that of placebo. A standardized exercise test was performed at 6 h and 12 h after dosing on the first and last day of each treatment period. Salmeterol produced significant protection against EIB at 6 and 12 h after the first dose in comparison with placebo, whereas there was no significant attenuation of EIB after 4 weeks of chronic treatment with salmeterol. The percentage fall in FEV1 after exercise challenge at 6 h was (first dose): placebo 34·8 ± 4·9% vs. salmeterol 11·9 ± 2·8% (P<0·05); (4 weeks): placebo 32·9 ± 5·3% vs. salmeterol 24·0 ± 4·4% (ns). These results suggest that tachyphylaxis may develop to the functional antagonism of salmeterol against EIB. © 1994.