List of products in the National Drug Code with proprietary name . Isosorbide mononitrate is used to prevent chest pain (angina) in patients with a certain heart condition (coronary artery disease). This medication belongs to a class of drugs known as nitrates. It works by relaxing and widening blood vessels so blood can flow more easily to the heart. This medication will not relieve chest pain once it occurs. Also, it is not intended to be taken just before physical activities (such as exercise or sexual intercourse) to prevent chest pain. Other medications may be prescribed by your doctor for these conditions. Consult your doctor for more details.