Fildena belongs to a class of drugs known as phosphodiesterase type 5 (PDE5) inhibitors. Its primary function is to help men with ED by improving blood flow to the penis, thus enabling an erection when sexually stimulated. It does this by inhibiting the enzyme PDE5, which is responsible for breaking down cGMP, a compound that helps relax smooth muscles and widen blood vessels in the penis. The result is improved erectile function and sexual performance.