Sildenafil, the active ingredient in Vigora 50 mg, inhibits the enzyme phosphodiesterase type 5 (PDE5). This inhibition increases levels of cyclic guanosine monophosphate (cGMP), leading to the relaxation of smooth muscle cells and dilation of blood vessels in the penis. This results in improved blood flow, which helps achieve and maintain an erection in response to sexual stimulation.

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