TIME-COURSE AND DURATION OF BRONCHODILATATION WITH FORMOTEROL DRY POWDER IN PATIENTS WITH STABLE ASTHMA

Background-Formoterol, a new beta2 agonist, is long and fast acting wh en given as an aerosol. The aim was to determine the onset and duratio n of bronchodilatation with formoterol as a dry powder compared with s albutamol dry powder and with placebo. Methods-Fifteen patients with s table asthma with a reversibility of 15% or more participated in a dou ble blind, within patient study. On five different days the patients r eceived formoterol 6 mug, 12 mug, or 24 mug, salbutamol 400 mug, or pl acebo in random order. Forced expiratory volume in one second (FEV1) w as measured 10 minutes before, 30 minutes after, and then every hour f or up to 12 hours after treatment. Specific airway resistance (sRaw) a nd specific airway conductance (sGaw) were measured immediately before and one, three, five, 10, 15, and 30 minutes after treatment. Results -Formoterol 12 mug and 24 mug caused bronchodilatation as rapidly as s albutamol 400 mug. 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 sustain ed for 9 hours and 16 minutes with salbutamol 400 mug, for 9 hours and 45 minutes with formoterol 6 mug, for 11 hours and 22 minutes with fo rmoterol 12 mug, and for 11 hours and 42 minutes with formoterol 24 mu g. Conclusions-Formoterol as a dry powder at doses of 12 mug and 24 mu g produces a rapid onset of action and has a bronchodilator effect com parable with salbutamol 400 mug as a dry powder. The bronchodilatation was sustained for 11-12 hours. Formoterol 6 mug caused similar bronch odilatation but more slowly and for a shorter time.