Arrhythmogenic effects of orally administered bronchodilators.

The respiratory and circulatory effects of orally administered ephedrine sulfate, 25 mg, aminophylline, 400 mg, terbutaline sulfate, 5 mg, and placebo were evaluated in 20 patients with ventricular arrhythmia by a double-blind crossover method. The bronchodilator effect of terbutaline was similar to that of aminophylline over four hours but superior to ephedrine at the fourth hour. Both terbutaline and ephedrine exhibited chronotropic effects, with the effect of terbutaline greater than that of ephedrine at the fourth hour. The effect of aminophylline on heart rate did not differ from placebo. Only terbutaline was associated with an increase in ventricular ectopic beats. Ventricular tachycardia occurred in three patients treated with terbutaline and in one patient with ephedrine. There were no significant changes in blood pressure. Orally administered terbutaline should not be regarded as safer than orally administered ephedrine or aminophylline in patients with arrhythmias.