Cenforce 100mg usa contains sildenafil citrate. This is called "Blue Pill", that helps male to cure erectile dysfunction. It is an oral medicine taken before 1-3 hours of sexual intimacy. Sildenafil is a PDE-5 inhibitor, a class of drugs used to treat erectile dysfunction. It works by prolonging the latency of ejaculation, thereby preventing the refractory period. It works by blocking an enzyme called PDE5, which breaks down cGMP, one of the essential chemicals needed for developing an erection. As a result, after sex, cGMP levels in the body are low, causing a weak or absent erection.