Fildena 100mg functions by increasing blood flow to the penis, a vital organ for achieving and maintaining an erection. Penile artery dilation and relaxation occur in response to sexual arousal in men. This allows for increased blood flow into the sponge-like corpus cavernosum. Sildenafil citrate, a PDE5 inhibitor, is the active ingredient in Fildena 150mg milligrams. It aids in inhibiting the enzyme responsible for chemical cGMP degradation.