Tadacip is an inhibitor of the PDE-5 enzyme in a man's body, just like other erectile dysfunction medications that include active components.
An erection occurs when a person is sexually stimulated. The smooth muscle in the corpus cavernosum and the arteries in the penis relax, increasing blood flow in the penis.

Nitric oxide released by endothelial cells and nerve terminals causes smooth muscle cells to produce more cGMP, which in turn causes an increase in blood flow.

This enzyme will prevent the creation of cGMP, which is necessary for males. The blood vessels will relax or enlarge once the penis is able to resume producing cGMP.