Avanafil Stendra. Teva sued to have the latter patent invalidated, but Pfizer prevailed in an August federal district court case. If your dose is different, do not change it unless your doctor tells you to do so. Ask your healthcare professional how you should dispose of any medicine you do not use. Common ones include: Flushing of the skin.Oral medicines for ED usually work well and cause few side effects. The four main medicines taken by mouth for erectile dysfunction are: Avanafil (Stendra). . Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise .  · Proper Use Drug information provided by: Merative, Micromedex ® Use sildenafil exactly as directed by your doctor. Do not use more of it and do not use it .