Pharmacotherapeutic Group: Antiangina pectoris. ATC Code: C01DA14, vasodilator used in cardiac diseases.
Pharmacology: Isosorbide mononitrate is an organic nitrate, a vasodilator which is common with other cardioactive nitrates. It produces decreased left and right ventricular end-diastolic pressures to a greater extent than the decrease in systemic arterial pressure; thereby, reducing afterload and especially, the preload of the heart.
Isosorbide mononitrate influences the oxygen supply to ischaemic myocardium by causing the redistribution of blood flow along collateral channels and from epicardial to endocardial regions by selective dilation of large epicardial vessels. It reduces the requirement of the myocardium for oxygen by increasing venous capacity causing a pooling of blood in peripheral veins; thereby, reducing ventricular volume and heart wall distension.
Pharmacokinetics: Isosorbide mononitrate is readily absorbed from the gastrointestinal tract. Following oral administration of conventional tablets, peak plasma levels are reached in 30 min to 1 hr; onset of actions occur within 20 min and lasts for about 8-10 hrs. Isosorbide mononitrate does not undergo first-pass hepatic metabolism and bioavailability is nearly 100%. Isosorbide mononitrate is widely distributed with a large apparent volume of distribution. It is taken up by smooth muscle cells of blood vessels, and the nitrate group is cleaved to inorganic nitrate and then to nitric oxide. Isosorbide mononitrate is metabolized to inactive metabolites. Only about 2% of isosorbide mononitrate is excreted unchanged in urine. An elimination half-life of about 4-5 hrs has been reported.