Forzest 20 mg contains tadalafil, which is a medication used to treat erectile dysfunction (ED) in men. Tadalafil belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors, which work by increasing blood flow to the penis during sexual stimulation, resulting in improved erectile function. Tadalafil, the active ingredient in Forzest 20 mg, works by inhibiting the action of PDE5, an enzyme that regulates blood flow in the penis. By blocking PDE5, tadalafil helps to increase the levels of cyclic guanosine monophosphate (cGMP), a chemical messenger that relaxes smooth muscles in the penis and increases blood flow, leading to an erection.