Also tell your doctor if you have or have ever had pulmonary veno-occlusive disease PVOD; blockage of veins in the lungs ; a stomach ulcer; heart, kidney, or liver disease; a heart attack; heart failure; angina chest pain ; an irregular heartbeat; a stroke; chest pain; high or low blood pressure; high cholesterol; a bleeding disorder; blood circulation problems; blood cell problems such as sickle cell anemia a disease of the red blood cells , multiple myeloma cancer of the plasma cells , or leukemia cancer of the white blood cells ; conditions affecting the shape of the penis e. Use only the brand of this medicine that your doctor prescribed. Age greater than 50 years or Coronary artery disease or Crowded disc or low cup to disc ratio in the eye an eye disorder or Diabetes or Hyperlipidemia high fats in the blood or Hypertension high blood pressure or Non-arteritic anterior ischemic optic neuropathy or NAION serious eye condition , history of or Smoking—May increase the chance for a serious side effect in the eye called NAION. This increased blood flow can cause an erection. However, the dose is usually not more than 80 mg 3 times a day. Children 1 year of age and older weighing 45 kilograms kg or more—20 mg 3 times a day. If too much is used, the chance of side effects is increased.Q&A Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription drug that’s used in . Typical dosing for Sildenafil (Viagra) The typical dose is to take 50 mg of sildenafil (Viagra) by mouth, about 1 hour before sex, as needed. The maximum recommended dose is mg. Don’t take sildenafil (Viagra) more than once daily (at any dose). Written by Brian Leonard, PharmD, BCACP, BCGP. 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.