Inclusion Criteria:

- Male, must be ≥ 18 years of age, with histologically confirmed prostate
adenocarcinoma, that is clinically localized to the prostate gland

- Stable sexual relationship for ≥ 6 months

- Open or laparoscopic bilateral nerve-sparing radical prostatectomy

- Baseline score of ≥ 22 on the International Index of Erectile Function Domain
(Appendix A)

- Able to speak, read and write in the English language

- Calculated creatinine clearance using the 4 variable MDRD equation based on serum
creatinine, age, race, and gender of > 60 cc/min

- Patient is able to walk up two flights of stairs briskly without chest pain

- Patient needs to have their baseline sitting AND standing blood pressure and pulse
done at the time of consent

Exclusion Criteria:

- Preoperative or planned postoperative pelvic radiation therapy

- Preoperative or planned postoperative androgen deprivation

- Presence of Peyronie's disease at baseline

- Presence of a penile prosthesis at baseline

- Resection of one or both nerve bundles at surgery

- Any contraindications to sildenafil:

- Patient is currently using nitrates;

- Presence of retinitis pigmentosa;

- Presence macular degeneration;

- MI or CVA within 3 months;

- Patient is currently using MAOI medications

- Patient is currently using penile self injection medication (Trimix, Bimix, or PGE-1)

- Patient requiring sildenafil for penetration

- Use of sildenafil within 30 days of consent