Formoterol compared with beclomethasone and placebo on allergen-induced asthmatic responses.

Formoterol is a new long-acting beta 2-agonist. We compared the protective effect of 24 micrograms formoterol with 200 micrograms beclomethasone and placebo on inhaled allergen-induced asthmatic responses in mild stable asthmatic subjects. We measured airflow rates, histamine airway responsiveness, cell counts from sputum and peripheral blood, and markers of lymphocyte and eosinophil activation. Adjustments were made for the confounding effect of bronchodilatation produced by formoterol in comparisons using a control inhalation of normal saline. Formoterol caused bronchodilation and inhibition of histamine airway responsiveness for at least 24 h. It completely inhibited the early asthmatic responses when beclomethasone had no effect. Control comparisons of the effect of formoterol and beclomethasone on the allergen-induced late asthmatic response and increase in histamine responsiveness showed each to be equally effective but not to inhibit the responses completely. Formoterol caused bronchodilation in addition to preventing bronchoconstriction. Both drugs inhibited the rise in serum eosinophil cationic protein 24 h after allergen, but neither inhibited the allergen-induced increases in sputum or blood eosinophils or CD25+ lymphocytes. These results suggest that formoterol modifies allergen-induced airway responses through functional antagonism rather than the inhibition of inflammatory cell infiltration.