Speeds of Action of Single Doses of Formoterol and Salbutamol Compared with Placebo in Reversing Methacholine-induced Bronchoconstriction

Abstract

We compared the speeds of action of two doses of the long actingβ-agonist formoterol (12μg and 24μg) with those of salbutamol (400μg) and placebo using a double-blind, randomized, cross-over study design in 16 asthmatic subjects. A methacholine test was used on four separate study days to produce a standardized degree of bronchoconstriction (a decrement in FEV1 ≥20%) and one of the study medications as dry powder was administered immediately afterwards via an AerolizerTMinhaler device. The speeds of recovery were estimated from measurements of FEV1 over the following 2–90 min. All active treatments produced significantly greater bronchodilation than placebo as early as 2 min after administration, and their peak effects within 10 min; and no significant differences were noted between them. Mean recovery times by 50% of the FEV1 decrement provoked by methacholine were significantly shorter for the active medications: 5.7 min (formoterol 24μg), 6.4 min (salbutamol 400μg), 10.2 min (formoterol 12μg), and 53.1 min (placebo); the respective times for recovery by 80% being 18.0, 17.4, 22.1, and 83.3 min. We conclude that single doses of the dry powder formulations of all three active treatments produce rapid and effective bronchodilation. This conclusion should not, however, be extrapolated to the regular use of these medications, since differential down-regulation and tachyphylaxis may then exert an influence.