Isosorbide dinitrate is used to prevent angina (chest pain) caused by coronary artery disease. It does not work fast enough to relieve the pain of an angina attack that has already started. Isosorbide dinitrate belongs to the group of medicines called nitrates. It works by relaxing the blood vessels and increasing the supply of blood and oxygen to the heart while reducing its work load. When used regularly on a long-term basis, this helps prevent angina attacks from occurring.