Side effects of isosorbide mononitrate extended-release tablets include abdominal pain, diarrhea, lightheadedness, dizziness and headaches, according to Drugs.com. Other side effects include unusual heart sound, troubled breathing, convulsions, chest tightness and unusual tiredness. In very rare cases, side effects can include dark urine, pale skin, rapid heart beat, and discolored fingernails, palms or lips.
Doctors prescribe isosorbide mononitrate to prevent angina attacks, or chest pains. The medication works by widening blood vessels for blood to flow through more easily and for the heart to pump more easily. Patients should use this medication regularly to prevent attacks, explains Drugs.com. Suddenly halting the use of isosorbide mononitrate can result in a serious angina attack. This medication does not relieve an attack once it happens.
People taking drugs to treat conditions such as pulmonary arterial hypertension or erectile dysfunction should not use isosorbide mononitrate. Patients showing early signs of a heart attack, or those who are allergic to nitroglycerin, isosorbide mononitrate or isosorbide dinitrate should also avoid using isosorbide mononitrate, states Drugs.com. To ascertain the safety of isosorbide mononitrate, patients who have low blood pressure, congestive heart failure or kidney disease should inform their doctors. Pregnant women and nursing mothers should also notify their doctors.