Acute Effect of Indenolol on Human Airways

Airways resistance and expiratory flow have been investigated in 6 healthy volunteers given single doses of indenolol, propranolol, atenolol and placebo in a randomized, double-blind, cross over study. The three active drugs significantly decreased the effort-induced rise in systolic pressure, and they also reduced the resting heart rate. The relative potency against exercise-tachicardia was propranolol greater than atenolol greater than indenolol. The double and triple product were significantly decreased, too, without any difference between the active treatments. After placebo or indenolol, an exercise-induced increase in the forced expiratory flow at low pulmonary volumes (MEF50 and MEF75) was observed. The two control beta-blockers caused a fall in exercise expiratory flow as compared to the resting values. The noncardioselective agent (propranolol) was more effective than the cardioselective compound (atenolol) in decreasing the expiratory flow. The mechanism of action of indenolol is discussed in the light of the lack of its acute effect on airways resistance.