Tadarise 20 tablets contain tadalafil, a phosphodiesterase type 5 (PDE5) inhibitor, used to treat erectile dysfunction(impotence) in men. When taken before planned sexual activity, tadalafil in Tadarise inhibit the breakdown (by the enzyme PDE5) of a chemical called cGMP, produced in the erectile tissue of the penis during sexual arousal, and this action allows blood flow into the penis causing an erection.