Tadacip 20 mg tablets belongs to the class of drugs known as phosphodiesterase-5 (PDE-5). When sexual stimulation occurs, Tadacip enables a man's penis to fill with enough blood to cause an erection. In men with erectile dysfunction a blood flow to the penis is not enough to produce erection. The main component of Tadacip is Tadalafil, it relaxes smooth muscles, widens blood vessels in the penis and this allows blood to fill cavernous bodies and result in erection. After sexual act erection disappears as in normal circumstances. Erection cannot be achieved by just taking Tadacip tablets, it requires sexual stimulation. Active substance of the medication is Tadalafil.