The active drug Sildenafil Citrate in the Fildena pill is an FDA approved chemical component. This drug falls in the category of PDE5 inhibitor drugs. Sildenafil Citrate in this medicine effectively acts as a reversible PDE5 enzyme antagonist. After consumption, it successfully works to inhibit the PDE5 (phosphodiesterase-5) enzyme. This enzyme is responsible for the degradation of important chemical cyclic GMP. Sildenafil Citrate halts the degradation of the cyclic Guanosine Monophosphate (cGMP). Once this process is stopped, nitric oxide is secreted at a higher level that boosts blood flow in the whole body and promotes the production of cGMP. Higher blood flow towards the penile organ occurs and helps a man to attain an erection. The effect of the Fildena anti-impotent pill lasts up to four to six hours.