The effect of inhaled salmeterol on methacholine responsiveness in subjects with asthma up to 12 hours.

The duration of the protective effect of 50 and 100 micrograms of inhaled salmeterol against methacholine-induced bronchoconstriction was compared with that of 200 micrograms of inhaled salbutamol in 12 patients with asthma with a baseline FEV1 of at least 70% and a provocative concentration of inhaled methacholine causing a 20% fall in FEV1 (PC20) greater than or equal to 8 mg/ml. The study was placebo controlled, double blind, randomized, and crossover. The bronchodilating effect was no longer significant 4 hours after inhalation of salbutamol, whereas the effect was still present 12 hours after administration of 50 and 100 micrograms of salmeterol. All active treatments caused PC20 to increase at 1 hour (p less than 0.05). PC20 (milligrams per milliliter) thus reached 3.7 +/- 0.8 after placebo, 13.8 +/- 3.0 after 50 micrograms of salmeterol, 23.2 +/- 4.7 after 100 micrograms of salmeterol, and 13.9 +/- 3.4 after 200 micrograms of salbutamol. The protective effect of 200 micrograms of salbutamol was no longer significant at 4 hours, whereas both doses of salmeterol protected against methacholine challenge up to 12 hours after inhalation (p less than 0.01). An increased incidence of tremor (2/12) and palpitations (2/12) was recorded after inhalation of 100 micrograms of salmeterol. We conclude that inhalation of 50 or 100 micrograms of salmeterol causes a long-lasting bronchodilatation and protects against methacholine-induced bronchoconstriction for at least 12 hours.

Time course of bronchodilating effect of inhaled formoterol, a potent and long acting sympathomimetic.

BACKGROUND: Most of the currently available inhaled beta 2 agonists are short acting bronchodilators. The aim of this study was to compare the rate of onset and duration of the bronchodilating activity of formoterol and salbutamol. METHODS: Fourteen patients with reversible airways obstruction received placebo, 200 micrograms salbutamol, and 12, 24, and 48 micrograms formoterol from a metered dose inhaler, according to a double blind, randomised crossover design. Forced expiratory volume in one second (FEV1) and specific airways conductance (sGaw) were measured over 12 hours. RESULTS: Salbutamol and all doses of formoterol caused a significant and substantial increase in sGaw one minute after inhalation. The mean maximum increase in FEV1 was 58% (8%) after 200 micrograms salbutamol compared with 63% (11%), 62% (10%), and 74% (10%) after 12, 24, and 48 micrograms formoterol, respectively. The mean maximum increase in FEV1 occurred 57 (12) minutes after administration of salbutamol compared with 137 (16), 141 (21), and 161 (33) minutes after 12, 24, and 48 micrograms formoterol respectively. The bronchodilating effect of salbutamol did not differ from placebo after six hours. In contrast, the mean increase in FEV1 12 hours after 12 micrograms formoterol (26% (8%) of baseline) significantly exceeded the change after placebo. Tremor was recorded in four patients after 48 micrograms formoterol. CONCLUSION: Formoterol is a potent, fast acting bronchodilator with a long duration of action.