Fildena 120 mg is a medication used for the treatment of erectile dysfunction (ED) in men. Sildenafil citrate inhibits the action of phosphodiesterase type 5 (PDE5), an enzyme present in the smooth muscle cells of the penis. By inhibiting PDE5, sildenafil allows the accumulation of cyclic guanosine monophosphate (cGMP), a chemical messenger. Increased cGMP levels lead to the relaxation of smooth muscle cells in the blood vessels of the penis.