The purpose of this study is to determine whether avanafil will affect different aspects of sperm production.

Inclusion Criteria:

• Provide written informed consent
• Able to produce semen samples without requiring therapy (PDE5 inhibitors, over-the-counter (OTC) medication, and/or herbal supplements) for erectile dysfunction
• Be medically healthy (no clinically significant screening results for medical history, electrocardiogram (ECG), laboratory studies, physical examination, etc.) in the opinion of the investigator
• Be willing and able to comply with all study requirements

Exclusion Criteria:

• An International Index of Erectile Function (IIEF) erectile function domain score of less than 17;
• History of infertility, vasectomy, testicular mass, testicular trauma, testicular abnormality (including size), radiation to the testis, previous pelvic surgery, cryotherapy of the prostate, known sperm defect, or retrograde ejaculation, or cryptorchidism;
• Resting heart rate <45 or >90 beats per minute at screening (3 rechecks permitted);
• Screening systolic blood pressure <90 or >140 mmHg and/or diastolic blood pressure <50 or >90 mmHg (3 rechecks permitted);
• High serum FSH (>18.0 mIU/mL), high serum LH (>18 mIU/mL), or low serum testosterone (< 270 ng/dL, early morning collection) on screening;
• AST or ALT >2.0 x ULN or other evidence of significant hepatic impairment;
• Prostate specific antigen (PSA) level ≥4 ng/mL at screening;
• Individuals who perform rotating shift work during the course of the study.