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. Read more on male sexual health on the Sexual Health Australia site. Sildenafil does not prevent pregnancy or the spread of sexually transmitted diseases such as human immunodeficiency virus HIV. Children younger than 1 year of age—Use and dose must be determined by your doctor. You just need to have one when you plan on engaging in sexual activity. Nitrates: Nitrates are medications which are used to treat or prevent heart pain caused by heart disease. You may take this medicine with or without food.Sildenafil comes as a tablet and suspension (liquid) to take by mouth. If you are taking sildenafil to treat erectile dysfunction, follow your doctor’s directions and the guidelines . 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 adult .