The active ingredient in Zenegra 100 mg, Sildenafil Citrate, is a phosphodiesterase type 5 (PDE5) inhibitor. PDE5 is an enzyme found in the blood vessels of the pill. By blocking PDE5, Sildenafil helps to relax the blood vessels in the pill, increasing blood flow and making it easier for the man to get and sustain an erection when sexually stimulated. It is important to note that Zenegra 100 mg only works when the person is sexually aroused and does not increase sexual desire itself. https://www.genericday.com/zenegra-100-mg.html