Bronchodilator and bronchoprotective effects of salmeterol in young patients with asthma.

BACKGROUND

In adults with asthma, the selective beta 2-adrenergic agonist salmeterol has a prolonged bronchodilator and bronchoprotective effect. To date, there are few published studies of salmeterol in children.

METHODS

We compared the bronchodilator and bronchoprotective effects of salmeterol, 25 and 50 micrograms, with salbutamol, 200 micrograms, and with placebo, administered via metered-dose inhaler, in a randomized, double-blind, within-patient, four-way crossover, single-dose study in 20 children.

RESULTS

Mean baseline forced expiratory volume in 1 second (FEV1) and PC20 methacholine were not significantly different (p > 0.05) on the 4 study days, and did not change significantly after placebo. FEV1 increased significantly from 5 to 30 minutes after salbutamol, and from 5 minutes to 12 hours after 25 micrograms or 50 micrograms salmeterol, compared with placebo. After 25 micrograms or 50 micrograms salmeterol, FEV1 was significantly lower than after salbutamol at 5 and 10 minutes, did not differ from salbutamol at 30 minutes, and was significantly greater than after salbutamol from 3 to 12 hours. No significant difference occurred between the effect of 25 micrograms salmeterol and the effect of 50 micrograms salmeterol on FEV1. After salbutamol, there was a significant increase in PC20 only at 30 minutes. After 25 micrograms or 50 micrograms salmeterol, PC20 increased significantly from 30 minutes to 12 hours. Salmeterol, 25 micrograms and 50 micrograms provided significantly greater bronchoprotection than salbutamol from 3 to 12 hours and from 30 minutes to 12 hours, respectively. Salmeterol, 50 micrograms, provided significantly better bronchoprotection than 25 micrograms salmeterol from 30 minutes to 12 hours. The amount of change in PC20 accounted for by change in FEV1 varied from 14% to 28%, indicating that protection against bronchoconstriction was not entirely dependent on bronchodilation.

CONCLUSIONS

Salmeterol is a potent, long-acting bronchodilator, with a slower onset of bronchodilation than salbutamol. It provides significantly greater and longer-lasting protection against bronchoconstriction than salbutamol.