Many people who buy Viagra also like to order tadalafil in the UK. This is because they work much in the same way, but Cialis tablets have a much longer lasting effect. Tadalafil is a PDE-5 inhibitor. PDE-5 or phosphodiesterase type 5 is an enzyme that is the body’s mechanism to allow the penis to return to its default flaccid state.

PDE-5 does this by degrading the compound cyclic guanosine monophosphate (cGMP). Cyclic GMP allows the penis to become erect through the process of Vasodilation. Vasodilation is the process wherein your smooth muscles and blood vessels relax and expand, allowing more blood to flow to the penis which results in an erection once you have been sexually stimulated.