Cenforce 100 contains the active substance (chemical component) Sildenafil Citrate, which belongs to a group of medicines called phosphodiesterase 5 (PDE 5) inhibitors. It works by helping to expand the blood vessels in the p*nis (over their entire length), thus increasing blood flow when you are s*xually aroused. Cenforce will only help you achieve an erection when s*xually stimulated.