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

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 Tulbuhaler(R) in patients with moderate asthma. Thirty-one patients (five women) with a mean forced expiratory volume in s (FEV1) of 1.97 +/- 0.541 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 mu g formoterol fumarate, on 5 separate days. Serial measurements of specific airways conductance (SGaw) and FEV1 were performed at regular time intervals for 12 h. The majority of the patients had at least a 50% increase in SGAW within 1-4 min after administration of all active treatments. The maximum increase in FEV1 over placebo was dose-dependent: 12% (6 mu g), 18% (12 mu g), 19% (24 mu g), and 26% (48 mu g) (P