Zhewitra 20 mg contains the active ingredient vardenafil, which is a phosphodiesterase type 5 (PDE5) inhibitor used to treat erectile dysfunction (ED) in men. Erectile dysfunction is a common condition characterized by the inability to achieve or maintain an erection sufficient for satisfactory sexual performance. Vardenafil works by inhibiting the enzyme phosphodiesterase type 5 (PDE5), which is responsible for the degradation of cyclic guanosine monophosphate (cGMP) in the corpus cavernosum of the penis. Increased levels of cGMP lead to smooth muscle relaxation and vasodilation, which enhances blood flow to the penis and facilitates an erection during sexual stimulation.