Sexual activity may be a strain on your heart, especially if you have heart disease. For treatment of erectile dysfunction: For oral dosage form tablets : Adults up to 65 years of age—50 milligrams mg as a single dose no more than once a day, 1 hour before sexual intercourse. Ask your doctor if you have any questions. It can be dangerous to take sildenafil if you also take medicines called nitrates often given for chest pain. What side effects can this medication cause? Children 1 year of age and older weighing 20 to 45 kg—20 mg 3 times a day. These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir.VIAGRA can cause your blood pressure to drop suddenly to an unsafe level if taken with certain other medicines. Do not take VIAGRA if you take any other medicines called “nitrates.” Nitrates are used to treat chest pain (angina). A sudden drop in blood pressure can cause you to feel dizzy, faint, or have a heart attack or stroke. Examples of Viagra’s more commonly reported side effects include: headache. flushing (temporary warmth, redness, or deepening of skin color) stuffy nose. indigestion (upset stomach) mild vision. AdMany Americans pay far too much for their prescriptions. We’re here to help. Saving is as easy as Join the millions of American who save every Credit Card Required · 5-Star Reviews · No Insurance RequiredThe lowest prices on specific drugs – Family Circle.