Isosorbide mononitrate is an organic nitrate with vasodilating properties. It is an anti-anginal agent that works by relaxing the smooth muscles of both arteries and veins, but but predominantly veins to reduce cardiac preload. Isosorbide mononitrate 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 workload. When used regularly on a long-term basis, this helps prevent angina attacks from occurring.