Inhaled dry-powder formoterol and salmeterol in asthmatic patients: Onset of action, duration of effect and potency

Abstract

Salmeterol and formoterol are two long-acting β2-agonists for inhalation, currently being used in clinical practice. The aim of the present study was to investigate the onset of action, duration of effect and potency of these two β2-agonists in asthmatic patients. Patients (n = 28) were included on the basis of salbutamol stepwise reversibility (100, 100 and 200 μg, given cumulatively; total reversibility ≤15%). In a double-blind placebo-controlled crossover study, the bronchodilating properties of formoterol 6, 12 and 24 μg were compared with the effects of salmeterol 50 μg. Formoterol was given via Turbuhaler® and salmeterol via Diskhaler®, and forced expiratory volume in one second (FEV1) was monitored during 12 h. Formoterol at all doses had a more rapid onset than salmeterol as judged from bronchodilation at 3 min after the dose. Formoterol at all doses had a similar duration of effect to salmeterol 50 μg, as judged from bronchodilation at 12 h after dose administration. When the relative potency of the two drugs was compared, salmeterol 50 μg was estimated to correspond to formoterol 9 μg (95% confidence interval: 3-19 μg). We confirm that formoterol and salmeterol are both long-acting β2-agonists, but with some differences in effect profile. We confirm the more rapid onset of action of formoterol compared with salmeterol, and furthermore, no difference in duration of effect is evident.