Verapamil and the myocardium.

Although many of the drugs which recently have been developed for use in relieving angina pectoris display β-adrenoceptor blocking activity this property cannot be essential, because verapamil relieves angina pectoris without blocking the cardiac β-adrenoceptors. Like propranolol, verapamil slows the heart and reduces both the peak tension developed during systole and the rate at which that tension is developed. Verapamil further resembles propranolol in that it improves cardiac efficiency, reduces the oxygen requirement of the heart and abolishes certain arrhythmias. Verapamil differs from propranolol, however, in that it does not antagonize the cardiac β-adrenoceptors and it dilates the coronary vessels. Verapamil probably owes its activity to its ability to interfere with the inwards displacement of calcium ions across cardiac cell membranes.