Duration of Protection by Inhaled Salmeterol in Exercise-induced Asthma

β-Adrenoceptor agonists such as albuterol are very effective in preventing exercise-induced asthma (EIA) when they are given as an aerosol immediately before exercise. However, their duration of protection against EIA is usually less than 2 h. This may be due partly to their rapid clearance from the airways. Salmeterol is a highly lipophylic compound that is thought to bind to an exoreceptor near the β-receptor. The objective of this study was to compare the protective effect of salmeterol with albuterol against EIA. Exercise was performed 0.5, 2.5, 4.5, and 6.5 hours after administration of the active drugs. Subjects attended the laboratory on four days within six weeks and cycled for 8 min breathing dry compressed air. We studied 17 asthmatic subjects (aged 19 to 49 years) with moderate to severe EIA. Salmeterol (50 μg) or albuterol (200 μg) was given from a metered dose inhaler via a spacer (Volumatic). On the control day, the mean work load ± 1 SD was 174 ± 47 W, ventilation (ve) was 77.9 percent ± 11.2 percent of the target ventilation (60 percent maximum voluntary ventilation [MVV]), and heart rate was 170 ± 14 beats per minute. This intensity was maintained for all tests. FEV1 was measured before and after exercise and was expressed as percent predicted and as percentage of the preexercise value (percentage of fall). Thirty minutes after treatment, both drugs were effective in inhibiting EIA—percentage of fall in FEV1, 17 ± 12 after salmeterol; percentage of fall in FEV1, 15 ± 15 after albuterol. At 2.5, 4.5, and 6.5 hours, the reduction in FEV1 was significantly less (p