AIRWAY RESPONSIVENESS AFTER A SINGLE-DOSE OF SALMETEROL AND DURING 4 MONTHS OF TREATMENT IN CHILDREN WITH ASTHMA

Background: Inhalation of a single dose of the long-acting beta(2)-adr enoceptor agonist salmeterol protects against methacholine-induced air way obstruction and other bronchoconstricting stimuli for at least 12 hours. Hypothetically, twice daily dosing of salmeterol may result in continuous protection. Objective: This study was designed to investiga te the protective effect of a single dose of salmeterol and of continu ous twice daily treatment on airway responsiveness to methacholine. Me thods: In a double-blind, parallel study, salmeterol 50 mu g twice dai ly was compared with salbutamol 200 mu g twice daily. Thirty children with mild asthma, who had little or no bronchial obstruction and were hyperresponsive to methacholine (PD20 less than or equal to 150 mu g) were allocated to receive either salmeterol of salbutamol. Airway resp onsiveness was measured before study entry, 12 hours after a single do se of drug was given, and monthly during 4 months of daily treatment. Measurements were always performed at the same time of the day, 12 hou rs after the last dose of medication was administered. Results: No sig nificant differences in FEV(1) were found between treatments at any ti me point. PD20 significantly increased after the first dose of salmete rol was given (geometric mean, 100 mu g). Geometric mean PD20 values w ere significantly better during salmeterol treatment than during salme terol treatment, 52 and 25 mu g, respectively (p = 0.0005). Conclusion : The protection provided by salmeterol during maintenance treatment w as less than that provided after the first dose (p < 0.001). However, protection did not diminish during the 4-month treatment period and re mained significant compared with paseline (p = 0.003).