Fildena 120mg works by inhibiting the enzyme phosphodiesterase type 5 (PDE5), which is responsible for the breakdown of cyclic guanosine monophosphate (cGMP) in the corpus cavernosum of the penis. By blocking PDE5, Fildena 120mg helps increase cGMP levels, which results in smooth muscle relaxation and improved blood flow to the penis during sexual stimulation. Ultimately, this mechanism results in a firm and sustained erection suitable for sexual activity.