Isosorbide mononitrate is a long-acting nitrate medication used to prevent angina (chest pain) in individuals with heart disease. It works by dilating blood vessels, improving oxygen delivery to the heart, and reducing its workload. Unlike quick-relief nitrates, isosorbide mononitrate is taken daily to help prevent angina episodes rather than treating them once they occur. This medication is commonly prescribed for patients with stable angina or coronary artery disease.