Sildenafil, the active ingredient, is a phosphodiesterase type 5 (PDE5) inhibitor. It works by increasing the levels of cyclic GMP, which relaxes blood vessels in the penis and enhances blood flow during sexual stimulation, helping achieve and maintain an erection.Onset and Duration: Fildena 120 mg typically starts working within 30 to 60 minutes. Its effects can last for about 4 to 6 hours, similar to other Sildenafil-based medications.