Dose response to inhaled salbutamol in chronic obstructive airways disease

Abstract

High dose inhaled salbutamol is increasingly used in the management of chronic obstructive airways disease. To determine the range of doses to achieve optimal bronchodilatation and the proportion of patients requiring high dose therapy we have studied 23 patients with chronic obstructive airways disease. Cumulative dose responses were measured to six incremental doses of salbutamol (0.2 to 1.2 mg) delivered by metered dose inhaler. Results were analysed by polynomial regression to calculate the smallest dose required to produce 90% maximal bronchodilatation in each patient. While 5/23 (22%) required > 1 mg the majority, 14/23 (61%), achieved 90% maximal bronchodilatation with salbutamol 0.6 mg or less. The 8 patients with severe airflow limitation (FEV1 ≤ 1 litre) showed a similar pattern of response. We conclude that in chronic obstructive airways disease there are wide individual variations in the dose of inhaled salbutamol producing 90% maximal bronchodilatation with only a minority requiring high dose therapy.