nitroglycerin
Nitroglycerin is a type of drug that relaxes (dilates) blood vessels and increases the supply of blood and oxygen to the heart while reducing its workload. "Nitro" is used to treat acute chest pain (angina), in which case it is prescribed as quick-dissolving pills to be placed under the tongue when needed. When the blood vessels dilate, blood flow to the tissues increases. This can relieve chest pain.
