Effect of inhaled budesonide on seasonal changes in sensitivity and maximal response to methacholine in pollen-sensitive asthmatic subjects.

The aim of this study was to investigate the effect of inhaled budesonide on modifications of the provocative concentration of agonist causing a 20% fall in forced expiratory volume in one second (FEV1) (PC20) and maximal response plateau to inhaled methacholine during the pollen season in pollen-sensitive subjects with mild asthma. The effects of inhaled budesonide (800 micrograms.day-1) on the threshold value (PC20) and maximal response plateau to inhaled methacholine were studied in 28 pollen-sensitive subjects with mild asthma during a pollen season in a randomized, double-blind, placebo-controlled parallel fashion. They were challenged with methacholine (up to 200 mg.ml-1) in February (preseasonal assessment) and during the middle of the pollen season (in May and again in June). Subjects treated with budesonide (n = 13) were protected from the decrease in PC20 seen in the placebo (n = 15) group (geometric mean PC20 placebo group: preseasonal = 8.51, May = 2.19 and June = 1.78 mg.ml-1; budesonide group: preseasonal = 3.71, May = 3.23 and June = 2.40 mg.ml-1; intergroup differences in doubling concentrations, p < 0.05). Among 10 subjects in the placebo group who reached plateau during the preseasonal assessment, seven lost the plateau in May and six in June. In the budesonide group, among seven subjects who reached plateau during the preseasonal assessment, three lost the plateau in May and four in June. Between-group differences were not significant. We conclude that in pollen-sensitive subjects with mild asthma, inhaled budesonide blocks the effects of natural allergen exposure on the methacholine threshold value.(ABSTRACT TRUNCATED AT 250 WORDS)