By inhibiting PDE5, sildenafil citrate helps to prolong the effects of cGMP, leading to relaxation of the smooth muscles in the penile arteries and corpus cavernosum. This relaxation allows for increased blood flow into the penis, resulting in an erection when a man is sexually stimulated.Fildena 120 mg is typically taken orally, with water, approximately 30 minutes to 1 hour before anticipated sexual activity.