This study evaluates the efficacy and safety of Udenafil dosed once a day 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

double-blind