Betamethasone valerate inhalation and exercise-induced asthma in adults.

The effect of regular inhalation of betamethasone valerate (800 microgram daily) on exercise-induced asthma has been studied in 18 adult patients. The active aerosol was compared with placebo in a double-blind cross-over study, each inhaler being used for four weeks. Exercise tests after each period of treatment were performed using a cycle ergometer, care being taken to match the oxygen uptake during exercise each time a patient was tested. Twelve patients experienced less exercise-induced fall in peak expiratory flow rate after the corticosteroid inhaler, while six did not. This effect appeared to be independent of any alteration in base-line lung function, suggesting that it was due primarily to diminution of bronchial hyperreactivity. It is suggested that this change may have been due to interference with the synthesis or release of mediator substances from mast cells.