INHALED CORTICOSTEROIDS DO NOT PREVENT THE DEVELOPMENT OF TOLERANCE TO THE BRONCHOPROTECTIVE EFFECT OF SALMETEROL

Introduction: Twice-daily inhaled salmeterol produces rapid reduction in its acute bronchoprotective effect against methacholine in patients with mild asthma. This investigation examined this effect in patients with moderate asthma who were using inhaled corticosteroids. Subjects and methods: Eight asthmatic volunteers who required inhaled corticos teroids for control of their symptoms and who were able to withhold tr eatment with beta(2)-agonists for 4 weeks before and during the study participated in a double-blind, crossover, placebo-controlled study wi th two random-order treatment periods: inhaled salmeterol, 50 mu g twi ce a day for seven doses, and placebo in similar fashion, with a 7-day or greater washout between these periods. Methacholine inhalation tes ts were done 1 h after doses 1, 3, 5, and 7, and then 24 h after the l ast dose of the study inhaler, 10 min post-200 mu g salbutamol. Result s: Baseline FEV(1) measurements before doses 3, 5, and 7 of salmeterol , ie, 12 h after salmeterol, were significantly higher than all other baseline values. Twenty-four hours after the last dose of salmeterol, the FEV(1) was no different from that during the placebo period. The g eometric mean methacholine concentration causing a 20% fall in FEV(1) (PC20) following the third dose of salmeterol (6.8 mg/mL) was signific antly lower than after the first dose of salmeterol (12.0 mg/mL; p=0.0 31), and this reduction of bronchoprotection persisted following doses 5 and 7. The methacholine PC20 10 min postsalbutamol measured after t he salmeterol period was significantly lower than after placebo (5.6 v s 13.3 mg/mL; p<0.001). Conclusions: Tolerance to the acute bronchopro tective effect of salmeterol was significant after the first two doses and persisted after the seventh dose. Tolerance to the acute bronchop rotective effect of salbutamol was also significant after regular use of salmeterol for seven doses. These effects, in subjects using inhale d corticosteroids regularly, were similar to those previously seen in patients with mild asthma using as-required beta(2)-agonists only, ind icating that tolerance is not prevented by use of inhaled corticostero ids.