Onset and duration of action of single doses of formoterol inhaled via turbuhaler ®

Abstract

The aim of the study was to investigate the time of onset and the duration of the bronchodilating effect of different doses of formoterol administered via Turbuhaler ® in patients with moderate asthma. Thirty-one patients (five women) with a mean forced expiratory volume in 1 s (FEV 1) of 1·97 ± 0·54 1 and a mean reversibility of 31 ± 14% of baseline were included in this double-blind, randomized, placebo-controlled and cross-over study. The patients inhaled single doses of placebo, i.e. 6, 12, 24, or 48 μg formoterol fumarate, on 5 separate days. Serial measurements of specific airways conductance ( SG aw) and FEV 1 were performed at regular time intervals for 12 h. The majority of the patients had at least a 50% increase in SG aw within 1–4 min after administration of all active treatments. The maximum increase in FEV 1 over placebo was dose-dependent: 12% (6 μg), 18% (12 μg), 19% (24 μg), and 26% (48 μg) ( P<0·001). Twelve hours after administration of 6, 12, 24, and 48 μg formoterol, the mean increase in FEV 1 was still 7%, 15%, 18% and 27%, respectively, above the value following placebo. Headache was the most frequently reported adverse event in all treatments including placebo. After inhalation of 48 μg, three patients experienced mild tremor lasting for less than 1 h; likewise, one patient experienced the same event for 3 h after placebo. Formoterol administered via Turbuhaler ® gave a rapid and dose-related bronchodilating effect lasting for 12 h and was well tolerated.