Salbutamol versus Atropine. Site of Bronchodilatation in Asthmatic Patients

The site of bronchodilatation produced by inhaled salbutamol (0.045 mg/kg) versus atropine (0.035 mg/kg) was investigated in 14 asthmatic young patients. No significant difference was found between the effects of the drugs on any of the large- or small-airway tests in those patients in whom bronchodilatation originated mainly in the large airways or when all patients were considered together. In those patients, however, in whom the small airways made the major contribution to the total airways resistance, atropine produced a higher increase in specific conductance, in maximal flow at all lung volumes and in density dependence of flow, but only the specific conductance showed a significant difference between the effects of the two drugs (p less than 0.01). It was concluded that in these patients atropine produced more bronchodilatation than salbutamol in both central and peripheral airways. These findings do not confirm previous studies which suggested that in asthmatic patients, as in normal subjects, atropine produces mainly central bronchodilatation, while salbutamol produces mainly peripheral bronchodilatation. The difference in doses, route of administration, time response and in the pretreatment severity and site of bronchodilatation could account for the disagreement between previous studies and the present one.