Nitroglycerin is one of a class of drugs called nitrates, and is the most commonly prescribed drug for chronic angina, the chest pain that accompanies coronary artery disease (CAD), the most common type of heart disease. In CAD, a fatty deposit called plaque builds up in the arteries that supply blood to the heart, causing them to become narrowed and stiff and reducing the flow of oxygen-rich blood to the heart muscle. This results in angina, and although it isnt a heart attack it can be a sign that youre at risk of one. Nitroglycerin works as a vasodilator-a drug that relaxes the blood vessels, enabling them to expand. This reduces the pumping force the heart has to exert to circulate blood through the body, thereby relieving the pain of angina.