Do not use Imdur if you are taking sildenafil (Viagra, Revatio). A dangerous drug interaction could occur, leading to serious side effects. You should not use Imdur if you are allergic to isosorbide mononitrate, isosorbide dinitrate, (Isordil, Dilatrate, Isochron), or nitroglycerin, or if you have early signs of a heart attack (chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling).

To make sure you can safely take Imdur, tell your doctor if you have any of these other conditions:

congestive heart failure;
low blood pressure; or
kidney disease.

Tell your doctor about all other medications you use, especially:

blood pressure medication;
dihydroergotamine (D.H.E. 45, Migranal) or ergotamine (Ergomar, Cafergot, and others);
an erectile dysfunction medication such as tadalafil (Cialis) or vardenafil (Levitra);
a beta blocker such as atenolol (Tenormin, Tenoretic), carvedilol (Coreg), labetalol (Normodyne, Trandate), metoprolol (Dutoprol, Lopressor, Toprol), nadolol (Corgard), propranolol (Inderal, InnoPran), sotalol (Betapace), and others;
heart or blood pressure medicine such as amlodipine (Norvasc, Caduet, Exforge, Lotrel, Tekamlo, Tribenzor, Twynsta, Amturnide), diltiazem (Cartia, Cardizem), nifedipine (Nifedical, Procardia), verapamil (Calan, Covera, Isoptin, Verelan), and others.

It is not known whether Imdur will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medication. It is not known whether isosorbide mononitrate passes into breast milk or if it could harm a nursing baby. Do not use Imdur without telling your doctor if you are breast-feeding a baby.

Call your doctor at once if you have a serious side effect such as:

fast, slow, pounding, or uneven heart rate;
feeling like you might pass out;
trouble breathing, blue-colored skin, tired feeling; or
worsening angina pain.

Less serious Imdur side effects may include:

headache, mild dizziness;
warmth, redness, or tingling under your skin;
nausea, vomiting, constipation, diarrhea;
pain or stiffness in joints or muscles;
hot flashes; or
dry mouth.