| Abstract: | The cardioequipotency of 400 mg bevantolol and 100 mg atenolol was determined by measuring the exercise heart rate in healthy subjects. The beta-blockers were then used in these doses to investigate their ventilatory effects in patients with asthma. The effects of both drugs on forced expiratory flow parameters for large and small airways were assessed at rest and during and after exercise. A dose-response curve was then plotted after inhalation of the beta 2-adrenoceptor agonist terbutaline. Bevantolol significantly decreased the forced expiratory volume in 1 second (FEV1) and the peak expiratory flow rate (PEFR) at rest, while there was no such change with placebo or atenolol. Both beta-blockers decreased the maximal expiratory flow rates at 50% of forced vital capacity (MEF50) and after expiration of 75% of the forced vital capacity (MEF25) at rest; the decrease was larger after bevantolol than after atenolol. During atenolol there was a decrease in FEV1 and in PEFR (P less than 0.01) 15 minutes after exercise in comparison with preexercise values. There was no significant difference between pre- and postexercise values of MEF50 and MEF25 during atenolol dosing. After bevantolol there was only a small change in PEFR after exercise, probably because of the low preexercise values of the ventilatory indices with this drug. Inhalation of terbutaline up to a dose of 2 mg significantly improved all ventilatory indices measured, but with bevantolol the values after 2 mg inhaled terbutaline were lower than the initial values.(ABSTRACT TRUNCATED AT 250 WORDS) |
