Tadalafil 20 mg is a medication used primarily to treat erectile dysfunction (ED) in men. Tadalafil works by inhibiting the enzyme PDE5, which regulates blood flow in the penis. By inhibiting PDE5, tadalafil increases blood flow to the penis during sexual stimulation, which helps men achieve and maintain an erection. Tadalafil is the active ingredient in Tadalafil 20 mg. It belongs to a class of medications called phosphodiesterase type 5 (PDE5) inhibitors.