Isosorbide Mononitrate

Isosorbide mononitrate is the major active metabolite of isosorbide dinitrate (ISDN), and most of the clinical activity of the dinitrate is attributable to the mononitrate. The principal pharmacological action of isosorbide mononitrate is relaxation of vascular smooth muscle, which leads to dilatation of the peripheral arteries and veins, especially the veins. Widening of the veins allows blood to pool in the periphery and reduces the amount returning to the heart, thereby lowering left ventricular end-diastolic pressure and pulmonary capillary wedge pressure (preload). Relaxation of the arterioles reduces systemic vascular resistance, systolic arterial pressure, and mean arterial pressure (afterload). The coronary arteries also dilate as a result of this action. How much each of these effects (preload reduction, afterload reduction, and coronary dilatation) contributes to the overall benefit is not yet clearly established.