Zudena 100mg : udenafil is a generic medication used to treat impotence, or erectile dysfunction, in men. Zudena 100mg tablets, which contain the phosphodiesterase type 5 inhibitor udenafil , are prescribed to men who suffer from impotence and erectile dysfunction. The most commonly reported adverse effects of Zudena tablets are lightheadedness or dizziness, headache, nausea, flushing, nasal congestion, and dyspepsia (heartburn). A few less frequent adverse effects include blurred vision, watery eyes from increased tear production, hypo- and hypertension, drowsiness, dyspnea (shortness of breath), and back and abdominal pain.