Bleeding disorders, history of or Stomach ulcer, or history of or—Chance of problems occurring may be increased. It is not known if the medicine is safe for use in these patients. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it. Avanafil Stendra. A newer form of the medicine that dissolves on the tongue might work faster than the pill that you swallow. Your doctor may adjust your dose as needed and tolerated. Check with your doctor immediately if any of the following side effects occur: Less common burning feeling in the chest or stomach burning, crawling, itching, numbness, prickling, “pins and needles”, or tingling feelings cloudy or bloody urine.Viagra (sildenafil) is a prescription drug that’s used to treat erectile dysfunction (ED). The drug comes as a tablet you’ll take by swallowing. It’s usually taken as needed about 1 . Viagra (sildenafil) is a phosphodiesterase-5 (PDE5) inhibitor used for the treatment of erectile dysfunction. What Are Side Effects of Viagra? Side effects of Viagra include: . Viagra Descriptions Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase .