Partial inhibition of the early and late asthmatic response by a single dose of salmeterol.

The long-acting beta 2-agonist salmeterol has been suggested to have other pharmacologic activities, that is, antiinflammatory capacities, in addition to its bronchodilator properties. We investigated the protective effect of 50 micrograms salmeterol in a placebo-controlled study on house dust mite-induced early- and late-phase reactions in 19 atopic asthmatic subjects. FEV1 and methacholine airway reactivity (AR) were measured. Eosinophils and their activation markers in peripheral blood were counted as indirect parameters of inflammation. Corrections were made for confounding of bronchodilator effects by salmeterol and the spontaneous diurnal variation, using saline inhalation as a control. Salmeterol completely inhibited the fall in FEV1 up to 10 h after the house dust mite challenge. Nevertheless, after correction, a biphasic response was present in the salmeterol group. Salmeterol protected against the allergen-associated increase in AR 3 h after the challenge, but no protection was observed after 24 h. Salmeterol did not inhibit the allergen-induced changes in total number of eosinophils and their activation markers in peripheral blood. These data suggest that a single dose of salmeterol modifies allergen-induced airway responses, above all by sustained bronchodilation.