When you take Fildena 50, the medicine will start working on the blocked bloodstream in the body. It works as a PDE-5 inhibitor in the body. Men will not be able to get an erection when there is no proper blood flow to the penile area. This happens if the PDE-5 enzyme stops the blood flow. Once the effect of the PDE-5 enzyme is reduced, then the blood will start flowing to the penile area. As the pressure increases, men will be able to get an erection.