How oral medicines differ Each oral medicine for ED has a slightly different chemical makeup. If it is not treated right away, priapism can permanently damage your penis sudden vision loss in one or both eyes. Generic versions of sildenafil, vardenafil and tadalafil are available. Avanafil Stendra. Kidney disease that needs to be treated with dialysis. Common ones include: Flushing of the skin. When oral medications might not be safe Check with your health care team before you take any medicine for erectile dysfunction.According to price-comparison site test1.ru, generic Revatio will cost you as little as $ per pill, depending on where you fill your prescription. That’s compared with . It’s available as a lower-cost generic. Reviewed by: Allison Barnes, PharmD. The list below does not include all possible drug interactions with Sildenafil (Viagra). Please note . 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 males* with .