Comparative study of the ventilatory effects of three beta 1-selective blocking agents in asthmatic patients.

A double blind, placebo-controlled study of the ventilatory effects of three new beta 1-selective adrenoceptor blockers was carried out in eight asthmatic patients. Measurements were performed before and 2, 3 and 4 h after ingestion of a single oral dose of placebo, atenolol 100 mg, metoprolol 100 mg or acebutolol 400 mg. At each time ventilatory indices and heart rate were assessed before, during and 15 min after an exercise test. The ventilatory indices were re-assessed after challenge with terbutaline 1.5 mg by inhalation. The three beta-blocking agents caused equal falls in exercise heart rate two hours after ingestion, indicating the equipotency of the cardiac effects. The three agents reduced significantly and to the same extent FEV1 and PEFR both before and after exercise. The respiratory indices clearly improved after stimulation with terbutaline. The response to terbutaline was less marked after acebutolol, which may indicate that it has a lower degree of beta 1-selectivity. The beta-blockers did not show any influence on bronchodilatation during exercise, or on exercise-induced bronchospasm.