Tadalafil, a phosphodiesterase type 5 inhibitor, is the active ingredient in Tadarise 40mg tablets, which are used to treat erectile dysfunction in males. During sexual stimulation, the erectile tissue of the penis releases nitric oxide, which activates the guanylate cyclase enzyme. An erection is brought on by this enzyme's elevation of the chemical cyclic guanosine monophosphate (cGMP), which relaxes the blood vessels in the penis and permits blood to fill the spongy erectile tissues.