Aspects of the cardiovascular pharmacology of exaprolol.

This study confirms that exaprolol is a potent beta-adrenoceptor antagonist, having a pA2 value of 9.8 for the inhibition of the inotropic and chronotropic responses of guinea-pig isolated atrial preparations to isoprenaline. In the anaesthetized cat, exaprolol blocks both the myocardial stimulatory and vasodilating effects of isoprenaline, suggesting that it is a non-selective antagonist at beta-adrenoceptors. Exaprolol also has direct electrophysiological effects on cardiac (Purkinje) tissue, reducing the rate of rise of phase 0 of the action potential. This direct action together with its marked blockade of beta-adrenoceptors may explain the drug's ability to markedly suppress the ischaemic ventricular arrhythmias that follow coronary artery occlusion in anaesthetized rats.