The penis is one of the areas where this enzyme works. Though it may seem like Sildenafil is the newbie ED medication on the block, there are no big reasons to prefer the more established Viagra product over generic Sildenafil. Keep out of the reach of children. Some medications should not be taken with sildenafil. All of these drugs are PDE5 inhibitors, so they all work in a similar way to Sildenafil and Viagra to help men with erectile dysfunction.Sildenafil tablets for erectile dysfunction come in different strengths ranging from 25mg to mg. The usual dose is 50mg, when you need it. Do not take it more than once a day. . 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 in .  · Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase .