CHANGES IN METHACHOLINE-INDUCED BRONCHOCONSTRICTION WITH THE LONG-ACTING BETA(2) AGONIST SALMETEROL IN MILD-TO-MODERATE ASTHMATIC-PATIENTS

Background-Beta-2 agonists protect against non-specific bronchoconstri cting agents such as methacholine, but it has been suggested that the protection afforded by long acting beta2 agonists wanes rapidly with r egular treatment. Methods-The changes in airway responsiveness were in vestigated during and after eight weeks of regular treatment with salm eterol 50 mug twice daily in 26 adult asthmatic patients, 19 of whom w ere receiving maintenance inhaled corticosteroids. The study was of a randomised, placebo controlled, double blind design. Airway responsive ness to methacholine was measured as PD20 by a standardised dosimeter technique 12 hours after the first dose, at four weeks and eight weeks during treatment (12 hours after the last dose of test medication), a nd at 60 hours, one week and two weeks after stopping treatment. Resul ts-There were no significant differences between the baseline characte ristics of the two groups. A significant improvement in PD20 was seen at all points during treatment with salmeterol compared with the place bo group, with no significant fall off with time. PD20 measurements re turned to baseline values after cessation of treatment with no signifi cant difference from the placebo group. Conclusions-Salmeterol gave si gnificant protection against methacholine induced bronchoconstriction 12 hours after administration. This protection was of small magnitude, but there was no significant attenuation with eight weeks of regular use and no rebound increase in airway responsiveness on stopping treat ment in a group of moderate asthmatic patients, the majority of whom w ere receiving inhaled corticosteroids.