Glyceryl trinitrate (nitroglycerin) ointment and isosorbide dinitrate: a review of their pharmacological properties and therapeutic use.

Sublingual glyceryl trinitrate (nitroglycerin) is the most widely used drug in the treatment of angina pectoris, but its use is limited due to its short acting effect. Recent investigations have shown that some longer acting nitrates administered orally or topically have a long acting antianginal effect. The mechanism of the antianginal effect of nitrates is multifactorial. Nitrates increase oxygen supply to the myocardium by causing redistribution of coronary blood flow. In addition, nitrates decrease myocardial oxygen demand by reducing left ventricular volume, intramyocardial tension, and left ventricular afterload. The use of nitrates for the treatment of congestive heart failure has also been established in recent years. Nitrates have a predominant venodilatory effect resulting in peripheral blood pooling and decreased venous return to the heart, thereby decreasing left ventricular filling pressure. The effect of nitrates on the arteriolar circulation is small, and there is usually little or no change in cardiac output. Some reduction in systemic blood pressure can be seen, while there is usually no change in heart rate. In a small number of patients with myocardial infarction complicated by congestive heart failure, the use of long acting nitrates has resulted in haemodynamic and symptomatic improvement. Nitrates has also bee shown to improve variant angina. Nitrates are usually well tolerated in most patients. However, some troublesome side effects can occur, including headache, postural hypotension, and methaemoglobinaemia.