Nitroglycerin transdermal patches (nitro patches) are used to prevent angina (chest pain) caused by narrowing of blood vessels in coronary artery disease (CAD). It does not work to relieve the pain of an angina attack that has already started. Nitroglycerin is a vasodilator; it works by relaxing the blood vessels (expanding the narrowed vessels) so that the heart does not need to work as hard.
