Verapamil inhibits the movement of calcium ions across cell membranes. The slow calcium ion current blocked by verapamil is more important for the activity of the sinoatrial node and atrioventricular node than for many other tissues in the heart. Verapamil decreases atrial automaticity, reduces atrioventricular conduction velocity, and prolongs the atrioventricular nodal refractory period. In addition, verapamil depresses myocardial contractility, reduces vascular smooth muscle tone, and dilates coronary arteries and arterioles in normal and ischemic tissues.