Nitroglycerin, also known as glyceryl trinitrate (GTN), is a vasodilator used for heart failure, high blood pressure, anal fissures, painful periods, treating the pain from esophageal spasm, and to treat and prevent chest pain caused by decreased blood flow to the heart (angina) or due to the recreational use of cocaine. This includes chest pain from a heart attack. It is taken by mouth, under the tongue, applied to the skin by cream or a patch, as a spray, or by injection into a vein.