The active ingredient in Vilitra, Vardenafil, works by inhibiting the action of phosphodiesterase type 5 (PDE5). PDE5 is an enzyme that breaks down cyclic GMP, a substance responsible for relaxing the smooth muscles in the penis and improving blood flow. By blocking PDE5, Vardenafil helps maintain high levels of cyclic GMP, leading to improved blood flow and making it easier for men to achieve and maintain an erection.