Sildenafil comes as a tablet and suspension liquid to take by mouth. Take sildenafil exactly as directed. This medicine works best when you take it on an empty stomach an hour before sex. Generic versions of sildenafil, vardenafil and tadalafil are available. 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.They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction (ED). Oral medicines for ED usually work well and cause few side . Viagra (sildenafil) is a brand-name prescription drug that’s used to treat erectile dysfunction (ED). Learn about side effects, warnings, dosage, and more. How to Get Generic Viagra An inexpensive blood pressure medication might be an option for some men who suffer from erectile dysfunction By Ginger Skinner Last updated: June .