Vardenafil works by increasing blood flow to the penis during sexual stimulation, thereby facilitating the achievement and maintenance of an erection. It does this by inhibiting the enzyme phosphodiesterase type 5 (PDE5), which is responsible for the breakdown of cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of the penis. Increased levels of cGMP lead to relaxation of the smooth muscles and dilation of the blood vessels in the penis, allowing for increased blood flow and an erection.

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