Udenafil  is the primary ingredient in zudena 100 mg tablet. The reaction to sexual stimulation is impacted by zudena.  Nitric oxide, a substance that is typically released in reaction to sexual excitement, is used to promote smooth muscle relaxation.  An erection results from the relaxation of the smooth muscles, which increases blood flow to certain parts of the penis.zudena is used to treat pulmonary arterial hypertension and male erectile dysfunction, or impotence. There are additional uses for zudena besides those mentioned above.