Erectile disorder is a situation wherein the penis does not harden and expand while a person is sexually excited, or whilst he can not preserve an erection. while a man is sexually stimulated, his frame's regular response is to growth blood flow to his penis to produce an erection. with the aid of controlling the enzyme, sildenafil enables to keep an erection after the penis is stroked. without physical movement to the penis, which include that occurring at some stage in sexual intercourse, sildenafil will no longer paintings to cause an erection.