Filagre is a PDE5 inhibitor, meaning it works by blocking the action of the PDE5 enzyme. This enzyme typically breaks down a substance called cGMP, which helps to relax and widen the blood vessels in the penis. When the PDE5 enzyme is inhibited, cGMP levels rise, leading to improved blood flow, which is essential for achieving an erection. Filagre only works in the presence of sexual stimulation, as it does not increase libido. It just helps with the physical process of achieving an erection by allowing blood to flow more easily into the penis.