Time course and duration of bronchodilatation with formoterol dry powder in patients with stable asthma

Abstract

Background - Formoterol, a new β2 agonist, is long and fast acting when given as an aerosol. The aim was to determine the onset and duration of bronchodilatation with formoterol as a dry powder compared with salbutamol dry powder and with placebo. Methods - Fifteen patients with stable asthma with a reversibility of 15% or more participated in a double blind, within patient study. On five different days the patients received formoterol 6 μg, 12 μg, or 24 μg, salbutamol 400 μg, or placebo in random order. Forced expiratory volume in one second (FEV1) was measured 10 minutes before, 30 minutes after, and then every hour for up to 12 hours after treatment. Specific airway resistance (sRaw) and specific airway conductance (sGaw) were measured immediately before and one, tree, five, 10, 15, and 30 minutes after treatment. Results - Formoterol 12 μg and 24 μg caused bronchodilatation as rapidly as salbutamol 400 μg. Peak values were not significantly different in the active treatments. The duration of action, calculated as median time with 20% or more of the maximum achieved increase in FEV1, was sustained for 9 hours and 16 minutes with salbutamol 400 μg, for 9 hours and 45 minutes with formoterol 6 μg, for 11 hours and 22 minutes with formoterol 12 μg, and for 11 hours and 42 minutes with formoterol 24 μg. Conclusions - Formoterol as a dry powder at doses of 12 μg and 24 μg produces a rapid onset of action and has a bronchodilator effect comparable with salbutamol 400 μg as a dry powder. The bronchodilatations was sustained for 11-12 hours. Formoterol 6 μg caused similar bronchodilatation but more slowly and for a shorter time.