The Efficacy and Safety of Udenafil in Patients With Erectile Dysfunction After Bilateral Nerve-sparing Radical Prostatectomy

Inclusion Criteria: * Male aged 20 or over 20 years and not more than 70 years who underwent bilateral nerve-sparing radical prostatectomy due to prostate cancer without metastasis * IIEF-EF score ≥22 at 1-8 weeks before bilateral nerve-sparing radical prostatectomy, and IIEF-EF ≤16 at screening visit * Presence of sexual partner from 8 weeks before bilateral nerve-sparing radical prostatectomy, and had planned to keep it during the trial * Agreed not to use any other erectile dysfunction medication (including both generic and specialty medicines) and other erectile dysfunction therapies during the trial period. * Patient agrees to voluntary participation and follow the instructions carefully, after fully hearing and understanding the details of this clinical trial Exclusion Criteria: * Patient who needs additional treatment in addition to bilateral nerve- sparing radical prostatectomy * Use Inhibitors of PDE-5 (Viagra®, Levitra®, Cialis®, Zydena®, Yaila®, Mvix® and Generic Medicines) or autologous injections of vasodilators or other erectile dysfunction therapies for erectile dysfunction within the first 8 weeks of bilateral nerve-sparing radical prostatectomy * If there is an uncontrolled diabetes (HbA1C\> 12%) at Visit 1 * If there is proliferative diabetic retinopathy at Visit 1 * If there is a history of CABG surgery, stroke, unstable angina, myocardial infarction, life-threatening arrhythmia, or heart failure within 6 months before the screening visit * History of spinal cord injury, non nerve-sparing radical prostatectomy or radical pelvic surgery * Hypotension below 90 / 50mmHg or uncontrolled hypertension above 170 / 100mmHg * Penis anatomic abnormalities (severe penile fibrosis, Peyronie's disease, etc.) * Presence of serious disability such as malignant tumor, lung, blood, endocrine system in Visit 1 * Patient who have active hepatitis B or C or who are infected with HIV virus * Patient who have genetic problems such as galactose intolerance, Lapp lactose dehydrogenase deficiency, glucose-galactose uptake disorder * Patient who have hyperprolactinemia or hypothyroidism * Serum AST and ALT are three times higher than normal upper limit * Serum Creatinine ≥ 2.5 mg / dl * Patient who have retinitis pigmentosa * Patient who have blood disease (sickle cell disease, multiple myeloma, leukemia) or bleeding disorder that can cause priapism * Patient with congenital QT prolongation syndrome or those taking a drug that increases QT interval * If the examiner considers that he / she is not suitable for participation in clinical trials, such as mental disorder or persistent abuse of medication * Patient who is taking Nitrate / Nitric oxide (NO) donor (Nitroglycerin, Sodium nitroprusside, Isosorbide mononitrate / dinitrate, Amyl nitrate / nitrite, etc.) * Patient who is taking Guanylate Cyclase stimulator (such as Riociguat) * Patient who is taking warfarin * Patient who is taking medications or foods that affect CYP3A4 metabolism * Metabolic inhibitors: Antibacterials (Erythromycin, etc.), Antifungals (Itraconazole, etc.), Antivirals (Ritonavir, Saquinavir, Amprenavir, Indinavir, Nelfinavir, etc.), H2 receptor antagonist (Cimetidine, etc), or grapefruit juice * Metabolic inducers: Dexamethasone, Rifampicin, Antipyretics (Phenytoin, Phenobarbital, Carbamazepine, etc.) * Patient who is taking androgens (Testosterone, etc.) or anti-androgens (5α-reductase inhibitors such as Finasteride, Dutasteride and anti- androgen hormones such as Flutamide and Bicalutamide) * Patient who is taking Trazodone * Patient who received other clinical trial medications (including placebo) within 4 weeks before the screening visit * History of hypersensitivity reactions to PDE-5 inhibitors (Viagra®, Levitra®, Cialis®, Zydena®, Yaila®, Mvix® and each Generic drug) * Patient who did not respond to PDE-5 inhibitors (Viagra®, Levitra®, Cialis®, Zydena®, Yaila®, Mvix® and each Generic drug) * Patient who has hypoactive sexual desire * If the examiner judges that it is not suitable for participation in this trial