Penegra, like the brand equivalent Viagra, contains the active ingredient Sildenafil Citrate. Sildenafil citrate is the archetype PDE-5 inhibitor which are class of medications designed for the treatment of ED. The way this medicine works is that it enters the bloodstream quickly and inhibits the action of the enzyme PDE5 in the body. When this happens, Nitric Oxide levels in the body increase which further improves the production of cGMP in the body. All this lead to dilation of the arteries and the relaxation of muscles at the penile region. This leads to a man to achieve a strong and hard erection which lasts for enough time to enjoy sexual intercourse.