Vidalista comprises of Tadalafil as the active elementthat is the third member of the phosphodiesterase type 5 (PDE-5) inhibitors class of drug. It is chemically and pharmacologically dissimilar from the other two members, namely Sildenafil citrate and Vardenafil. However, it has similar mechanism of action like Sildenafil citrate and Vardenafil. The active compound in it helps to block the action of the enzyme PDE-5 that regulates the penile erections. When the level of PDE-5 increases, it is known to cause restricted flow of blood in the penile region and that results in ED. Blockade of PDE-5 leads to increased levels of the biochemical nitric oxide and guanylylcyclase enzyme. These biochemicals cause elevated synthesis of cGMP in the body, in the penile region. The cGMP enzyme is known to cause vasodilation. Thus, increased production of cGMP leads to widening of blood vessels that carry the blood to the penis from the heart.