Bronchodilation and beta 2-selectivity of broxaterol in asthmatics: a crossover, single-blind, terbutaline- and placebo-controlled study.

To investigate the beta 2-receptor selectivity of a new beta 2-adrenoceptor agonist, broxaterol, we compared the respiratory and cardiovascular effects of this compound with those of terbutaline and placebo. Twelve asthmatic patients were evaluated in a randomized, single blind, crossover study. A single dose of each study treatment (broxaterol 400 micrograms and terbutaline 500 micrograms was administered with metered dose inhalers. Measurements of lung function (vital capacity, forced expiratory volume in one second, airway resistance and specific airway conductance), heart rate and systolic/diastolic blood pressure were performed before and at 15, 30, 60, 120, 240 and 360 min after each study treatment. No significant difference was observed between broxaterol and terbutaline in VC, FEV1 and Raw changes, although a greater and significant increase in sGaw was found only with broxaterol. Significant increases in heart rate and systolic blood pressure were observed only with terbutaline. The results of this study suggest that broxaterol can promote a greater bronchodilator effect with less cardiovascular side effects than terbutaline, probably through a greater beta 2-receptor selectivity.