Objective - To examine the effect of bronchodilator treatment given continuously versus on demand on the progression of asthma and chronic bronchitis and to compare the long term effects of a (beta-2 adrenergic drug (salbutamol) and an anticholinergic drug (ipratropium bromide). Design - Two year randomised controlled prospective crossover study in which patients were assigned to one of two parallel treatment groups receiving continuous treatment or treatment on demand. Setting - 29 general practices in the catchment area of the University of Nijmegen. Patients - 223 patients aged greater-than-or-equal-to 30 with moderate airway obstruction due to asthma or chronic bronchitis, selected by their general practitioners. Interventions - 1600-mu-g salbutamol or 160-mu-g ipratropium bromide daily (113 patients) or salbutamol or ipratropium bromide only during exacerbations or periods of dyspnoea (110). No other pulmonary treatment was permitted. Main outcome measures - Decline in ventilatory function and change in bronchial responsiveness, respiratory symptoms, number of exacerbations, and quality of life. Results - Among 144 patients completing the study, after correction for possible confounding factors the decline in forced expiratory volume in one second was -0.072 1/year in continuously treated patients and -0.020 1/year in those treated on demand (p < 0.05), irrespective of the drug. The difference in the decline in patients with asthma was comparable with that in patients with chronic bronchitis (asthma: 0.092 v -0.025 1/year; chronic bronchitis: -0.082 v 0.031 1/year). Bronchial responsiveness increased slightly (0.4 doubling dose) with continuous treatment in chronic bronchitis, but exacerbations, symptoms, and quality of life were unchanged. Salbutamol and ipratropium bromide had comparable effects on all variables investigated. Conclusions - Continuous bronchodilator treatment without anti-inflammatory treatment accelerates decline in ventilatory function. Bronchodilators should be used only on demand, with additional corticosteroid treatment, if necessary.
