PRECAUTIONS: Before taking isosorbide mononitrate, tell your doctor or pharmacist if you are allergic to it; to other nitrates (e.g., nitroglycerin) or nitrites; or if you have any other allergies. This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: recent head injury (increased intracranial pressure), severe anemia, certain severe stomach/abdominal diseases (hypermotility, malabsorption). Before using this medication, tell your doctor or pharmacist your medical history, especially of: low blood pressure, loss of body fluids (dehydration), certain heart conditions (e.g., cardiomyopathy, recent heart attack), current occupational exposure to nitrates, overactive thyroid. This drug may make you dizzy; use caution engaging in activities requiring alertness such as driving or using machinery. Limit alcoholic beverages and avoid overheating which can aggravate dizziness. To minimize dizziness and lightheadedness, get up slowly when rising from a seated or lying position. Caution is advised when using this drug in the elderly because they may be more sensitive to its side effects, especially dizziness and lightheadedness which could increase the risk of falls. This medication should be used only when clearly needed during pregnancy. Discuss the risks and benefits with your doctor. It is not known whether this drug passes into breast milk. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: This drug should not be used with the following medications because very serious (possibly fatal) interactions may occur: drugs to treat impotence (sildenafil, tadalafil, vardenafil). If you are currently using any of these medications, tell your doctor or pharmacist before starting isosorbide mononitrate. Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: drugs that lower high blood pressure (e.g., beta-blockers, calcium channel blockers, "water pills"/diuretics), certain migraine drugs (ergot alkaloids such as ergotamine). This product can affect the results of certain lab tests (blood cholesterol level). Make sure laboratory personnel and your doctors know you use this drug. Do not start or stop any medicine without doctor or pharmacist approval.