The pharmacologic effect of aerosolized terbutaline sulfate in exercise-induced bronchospasm

Bronchospasm can be induced in asthmatics when exercised according to a multistage branching treadmill protocol that allows them to achieve 80 per cent of maximal age-predicted heart rate. This degree of exercise is usually achievable and allows inducible bronchospasm to occur. This present study was undertaken to investigate the effect of terbutaline sulfate aerosol in exercise-induced broncho-spasm. Asthmatics were exercised to 80 per cent of their maximal heart rate, and FEV1.0 and MMEFR were assessed while standing using a Jones Pulmonar II waterless spirometer at 5, 15, and 30 minutes after exercise. After a standard rest period defined by a return to baseline of FEV1.0, MMEFR, and heart rate for 30 minutes, the subjects were administered either 0.50 mg aerosolized terbutaline sulfate or placebo and then exercised again. The pulmonary function parameters were again recorded after this exercise. Preterbutaline and postplacebo exercise resulted in a significant reduction in FEV1.0 and MMEFR, while after treatment with terbutaline not only did bronchospasm not occur but bronchodilation occurred (P less than 0.01). Inhaled terbutaline appeared to normalize the exercise tolerance of the asthmatics and restore physiologic pulmonary airway conductance according to the parameters of FEV1.0 and MMEFR.