Research Evaluating an Investigational Medication for Erectile Dysfunction - Post-Prostatectomy

Inclusion Criteria: * Adult males ≥ 18 years and ≤ 70 years; * Have a history of erectile dysfunction of at least 6 months duration following bilateral nerve-sparing retropubic radical prostatectomy; * Have a PSA level consistent with the absence of prostate cancer; * Have a history of sexual potency prior to radical prostatectomy without requiring medical therapy; * Be in a monogamous, heterosexual relationship with their current partner for at least 3 months; * Provide written informed consent; * Agree to make at least 4 attempts at intercourse per month; * Agree not to use any other treatments for erectile dysfunction; * Be willing and able to comply with all study requirements (including scheduled study visits, treatment plans, laboratory tests and other study procedures). Exclusion Criteria * Allergy or hypersensitivity to PDE5 inhibitors or any of the components of these drug products; * History of dose-limiting AEs during prior treatment with a PDE5 inhibitor or discontinued use of a PDE5 inhibitor due to lack of efficacy at the highest tolerated dose; * Concomitant use of one or more of the following medications: * Any nitrate, trazodone, itraconazole, ketoconazole, erythromycin, or cimetidine; * Other prescription or OTC drugs that are known to interfere with metabolism by the CYP 3A4 enzyme; * If receiving hormone replacement therapy (including thyroid supplementation), dose that has not been stable for at least 3 months; * If treated with an alpha blocker, dose that has not been stable for at least 14 days; * Erectile dysfunction as a consequence of advanced neurologic disease, spinal cord injury, or diabetes; * History of severe erectile dysfunction requiring medical therapy prior to bilateral nerve-sparing radical prostatectomy; * History of previous pelvic surgery, brachytherapy, or cryotherapy of the prostate; * Sexual partner who is under 18 years of age, pregnant, intends to become pregnant during the course of the study, is breastfeeding, has dyspareunia or other gynecologic conditions or other major medical conditions that would interfere with sexual activity or would have difficulty complying with study requirements; * Uncontrolled hypertension; * Hypotension; * Orthostatic hypotension; * Myocardial infarction, stroke, life-threatening arrhythmia or coronary revascularization within the past 6 months; * Unstable angina, angina with sexual intercourse, or congestive heart failure \> NYHA Class II; * History or ECG evidence of any high-risk arrhythmia or clinically significant ECG; * Hypertrophic, obstructive, or other clinically significant cardiomyopathy, moderate or severe cardiac valvular disease; * Type 1 or type 2 diabetes, history of use of any antidiabetic medication; * Clinically evident penile lesions, abrasions, anatomical deformities such as penile fibrosis, Peyronie's disease, penile implants, urinary tract or bladder infection, or sexually transmissible disease that the investigator deems to be clinically significant; * Condition(s) predisposing to priapism, such as sickle cell disease , multiple myeloma, or leukemia; * Any malignancy other than carcinoma of the prostate (except basal cell carcinoma or squamous cell carcinoma of the skin); * Prior use of, or likely to require radiotherapy, chemotherapy, androgen deprivation therapy, cryotherapy, non-nerve-sparing surgery, and/or bladder or penile surgery during the study; * Evidence of significant hepatic impairment; * On dialysis, or history of renal transplantation; * Untreated hypogonadism or low serum total testosterone; * Abnormal laboratory value(s) judged to be clinically significant by the investigator; * Positive STD screen (syphilis, gonorrhea, or chlamydia); * Positive for HIV, HCV Ab, or HBsAg at screening; * History or current drug, alcohol, or substance abuse; * Positive urine drug screen; * Positive breath alcohol test; * Retinitis pigmentosa or nonarteritic anterior ischemic optic neuropathy; * Use of any treatment or device for treatment of erectile dysfunction; * Use of any other investigational medication or device for any indication within 30 days prior to enrollment or at any time during this study; * Previous participation in any other investigational study of avanafil; * Any history of bipolar disorder or psychosis, greater than one lifetime episode of major depression, current depression of moderate or greater severity or antidepressant use that has not been stable for at least 3 months; * Involvement in the planning and conduct of the study on the part of subject or partner; * Evidence of any clinically significant medical, psychiatric, social or other condition by history, physical examination or laboratory studies that, in the opinion of the investigator, would contraindicate the administration of study medications, affect compliance, interfere with study evaluations, limit study participation, contraindicate sexual activity or confound the interpretation of study results.