Dose-response study of inhaled salmeterol in asthmatic patients with 24-hour spirometry and Holter monitoring.

Salmeterol is a new long-acting beta 2-selective adrenoceptor agonist. In this double-blind, 6-way crossover study, four single doses of salmeterol by metered dose inhaler (12.5, 25, 50, 100 micrograms) were compared with albuterol aerosol 200 micrograms and placebo in 24 patients with moderate asthma with 24-hour pulmonary function testing and Holter monitoring. Salmeterol was an effective bronchodilator at each dose evaluated and demonstrated a greater increase in FEV1 above baseline, a slightly slower onset and a longer duration of bronchodilation than albuterol. Median durations of bronchodilation were 9.0, 15.6, 13.4, and 18.4 hours with increasing doses of salmeterol in comparison to 4.2 hours for albuterol. Holter monitoring showed (1) a mean maximum heart rate 2 to 5 bpm higher after salmeterol 50 and 100 micrograms compared with placebo and (2) supraventricular premature beats (> 30 per hour or > 100 per 24 hours) more often in the salmeterol 100-micrograms group (13% to 17% of patients) than in the placebo (4%), albuterol (4% to 8%), or other salmeterol groups (4% to 9%). These differences were not statistically significant. Tremor and palpitations were the most frequently reported drug-related adverse events and their frequencies increased with increasing doses of salmeterol. This study demonstrated that single doses of salmeterol given by metered dose inhaler over an 8-fold range possess substantial, long-lasting bronchodilator activity.