Viagra (sildenafil citrate) is an anti-impotence medicine that has been specially designed to help people unable to get an erection to complete sexual intercourse and regain their sexual power. Viagra is efficient in 80% of all cases treating impotence in men with even very severe sexual disabilities. Make sure you never take Viagra more often than once every 24 hours to avoid an overdose. Never combine it with isosorbide mononitrate, nitrates and isosorbide dinitrate, as this may lead to a dangerous sudden drop in blood pressure. Make sure you talk to your doctor before starting the treatment and report any medical conditions you have which may interfere with the effects of Viagra, especially coronary artery disease, blood cell disorder, kidney disease, heart attack, history of a stroke, abnormal blood pressure, bleeding disorder, and stomach ulcer. Mild side effects such as stuffy nose, upset stomach, back pain, memory problems, headache, warmth or redness in your face, neck, and some other ones are common at the beginning of the treatment. If they change in intensity, call your doctor about them; otherwise just carry on with the treatment making sure you follow all the directions provided.