Effect of a single dose of salmeterol on the increase in airway eosinophils induced by allergen challenge in asthmatic subjects

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Abstract
BACKGROUND The long acting β2 agonist salmeterol is very effective in preventing asthmatic responses to specific stimuli, and this effect could theoretically be due to some anti-inflammatory property in addition to bronchodilator property. METHODS The protective effect of a single dose of salmeterol (50 μg) on allergen induced early and late responses and on the associated airway inflammation was investigated in a double blind, placebo controlled, crossover study in 11 atopic asthmatic subjects. Eosinophil percentages and concentrations of eosinophil cationic protein (ECP) in peripheral blood and in hypertonic saline induced sputum were measured 24 hours after allergen inhalation. RESULTS Salmeterol effectively inhibited both early and late asthmatic responses in comparison with placebo. Salmeterol also inhibited the increase in the percentage of eosinophils in the sputum 24 hours after allergen inhalation (median (range) baseline 6% (1–36), after placebo 31% (5–75), after salmeterol 12% (1–63)). However, the increase in both sputum and serum ECP concentrations 24 hours after allergen challenge was not affected by pretreatment with salmeterol. CONCLUSIONS A single dose of salmeterol inhibits the allergen induced airway responses and the increase in sputum eosinophils after allergen challenge.