Continuous and on demand use of bronchodilators in patients with non-steroid dependent asthma and chronic bronchitis: four-year follow-up randomized controlled study.

Abstract

BACKGROUND. A previous two-year study of continuous and on demand bronchodilator therapy in patients with moderate asthma and chronic bronchitis showed a deterioration in lung function in those on continuous therapy. AIM. A two-year follow-up study was undertaken of patients who had been shown in the previous study to have non-steroid dependent (mild) asthma and chronic bronchitis, in order to investigate the effect of continuous and on-demand treatment with bronchodilator therapy. METHOD. Patients for the study were drawn from 29 general practices in the catchment area of the University of Nijmegen, the Netherlands. A total of 83 patients (27 with asthma and 56 with chronic bronchitis) were selected from a group of 160 patients who had completed the previous two-year bronchodilator trial. During these first two years the selected subjects had been shown to be non-steroid dependent (no rapid decline in lung function and a low number of exacerbations of their condition per year), and they were followed up for another two years of treatment with bronchodilator therapy. At the start of the four-year study, patients were randomly assigned to one of two parallel treatment groups: continuous treatment (dry powder inhalations of either salbutamol 1600 micrograms or ipratropium bromide 160 micrograms daily) or treatment on demand (only during exacerbations or periods of dyspnoea). Outcome parameters were the annual decline in lung function, changes in peak flow rate, bronchial hyper-responsiveness, exacerbation rate, respiratory symptoms and reported health. RESULTS. After correction for possibly confounding variables and for regression to the mean, the decline in lung function was 49 ml year in patients taking bronchodilators continuously and 51 ml year in patients using bronchodilators on demand, irrespective of the drug use. Continuously treated patients, whether suffering from asthma or chronic bronchitis, did not differ from patients treated on demand with respect to mean morning peak flow rate, diurnal (and week to week) variation of the peak flow rate, bronchial hyper-responsiveness, exacerbation rate and reported health. There was no difference between the long-term effects of salbutamol and ipratropium. CONCLUSION. Continuous use of bronchodilators over four years in patients with non-steroid dependent asthma or chronic bronchitis does not increase the decline in lung function which had been observed previously in patients with moderate asthma or chronic bronchitis during two years of continuous treatment with bronchodilators.