ATC Group: C08D Selective calcium channel blockers with direct cardiac effects

Diltiazem is a calcium antagonist. It restricts the slow channel entry of calcium into the cell and so reduces the liberation of calcium from stores in the sarcoplasmic reticulum. This results in a reduction of the amount of available intracellular calcium reducing myocardial oxygen consumption.

Verapamil is a phenylalkylamine calcium antagonist which blocks the inward movement of calcium ions in cardiac muscle cells, in smooth muscle cells of the coronary and systemic arteries and in cells of the intracardiac conduction system. It lowers heart rate, increases myocardial perfusion and reduces coronary spasm. Because of its effect on the movement of calcium in the intracardiac conduction system, verapamil reduces automaticity, decreases conduction velocity and increases the refractory period.