A high dose of albuterol does not overcome bronchoprotective subsensitivity in asthmatic subjects receiving regular salmeterol or formoterol

Abstract

Background: Regular treatment with inhaled, long-acting β₂ -agonists is associated with subsensitivity for bronchoprotective effects. It is not known whether a high dose of short-acting β₂ -agonist could overcome this subsensitivity. Objectives: The objective of this study was to investigate the acute effects of a high dose of inhaled albuterol on methacholine-induced bronchoconstriction in patients receiving regular treatment with salmeterol or formoterol. Methods: Ten stable asthmatic subjects (mean age, 34 years; FEV₁ , 77% of predicted value), all taking inhaled corticosteroids (methacholine PD₂₀ < 500 μg), were recruited into a randomized, single-blind, crossover study. After an initial 1-week run-in period, subjects underwent 3 separate treatment periods each of 9 days (separated by a washout of at least 5 days) comprising inhaled placebo twice daily, inhaled salmeterol dry powder 50 μg twice daily, or inhaled formoterol dry powder 12 μg twice daily. Methacholine challenge was performed 1 hour after the first dose and after 7 days of treatment. After 9 days of treatment, a third methacholine challenge was performed 1 hour after inhalation of a single 1600 μg dose of albuterol dry powder. Results: There was significant (P < .001) improvement in geometric mean PD₂₀ after the first dose of active treatment as compared with placebo (78 μg) versus salmeterol (266 μg, a 3.4-fold difference [95% CI 1.9 to 6.1]) and versus formoterol (318 μg, a 4.1-fold difference [95% CI 2.3 to 7.3]). This bronchoprotection diminished with regular treatment, although it remained significant (P < .01) compared with placebo (68 μg) versus salmeterol (144 μg, a 2.1-fold difference [95% CI 1.2 to 3.8]) and versus formoterol (230 μg, a 3.4-fold difference [95% CI 1.9 to 6.2]). After 9 days, the protection afforded by a single dose of albuterol after placebo pretreatment (889 μg) was significantly (P = .005) higher in comparison with albuterol protection after salmeterol pretreatment (338 μg, a 2.7-fold difference [95% CI 1.1 to 6.8]) and after formoterol pretreatment (247 μg, a 3.6-fold difference [95% 1.4 to 9.1]). Conclusions: Thus in stable asthmatic subjects receiving regular salmeterol or formoterol, bronchoprotective subsensitivity was not overcome by administering a high dose of albuterol. Further studies are required to evaluate the clinical relevance of this pharmacologic phenomenon when albuterol is used in acute asthma. (J Allergy Clin Immunol 1999;103:88-92.)