L-Arginine Supplementation With or Without Enzyme Inhibitors Treating Erectile Function of Prostate Cancer Survivors

INCLUSION CRITERIA: * Male prostate cancer survivor previously treated with radiotherapy and who identifies himself as concerned with sexual quality of life, including erectile dysfunction. (seed implants are eligible) * Had successful sexual activity prior to the commencement of radiotherapy. * Erectile dysfunction, defined as inability to achieve or maintain an erection sufficient for satisfactory sexual performance * Interested in sexual activity and agrees to make at least one sexual intercourse attempt with a partner every week during the study. * The usage of PDE-5 inhibitors will be voluntary and will serve as a stratification factor. Patients taking PDE-5 inhibitors must agree to assume the responsibility for the cost of PDE-5 inhibitor treatment during the protocol period (8 week period) as this is not covered in the cost of the trial. * Patients currently taking PDE-5 inhibitors sildenafil (Viagra®, Pfizer Pharmaceuticals), tadalafil(Cialis®, Lilly ICOS, LLC), and vardenafil (Levitra®, Bayer Healthcare / Schering Plough Corp.)must agree to take the medication only as prescribed by their treating physician. * Patients taking PDE-5 inhibitors as part of this study must be on a stable dose of drug for at least one month prior to study entry. * Must be able to take oral medications. * \> 6 months following completion of all cancer therapy * No evidence of prostate cancer * Prior malignancies allowed if no evidence of recurrent disease. * If previously taken LHRH agonist androgen suppression (e.g, Lupron, Zoladex), anti-androgen (e.g., Casodex, Eulexin, Nilandron), or estrogenic (e.g., diethylstilbestrol) agents, serum testosterone must have returned to the laboratory normal range * No planned surgery while on protocol or for 4 weeks following completion of protocol * Prior cystoscopy is permitted. * Age \> 18 * ECOG performance status 0/1. * Patients must agree not to start taking an herbal product for erectile dysfunction during the eight weeks of study intervention. EXCLUSION CRITERIA: * No other concurrent erectile dysfunction therapies permitted (i.e. vacuum pump,cavernosal injections, and other drug therapies). Past use of these and other therapies permitted if the patient can meet the inclusion criteria above. * No testosterone supplementation permitted. * Use of LHRH agonist androgen suppression (e.g, Lupron, Zoladex), anti- androgen (e.g., Casodex,Eulexin, Nilandron), or estrogenic (e.g., diethylstilbestrol) agents within the last 6 months. * Prior prostate or lower genitourinary surgery (bladder, penis, urethra, testicles)including transurethral resection of prostate (TURP). (Prior vasectomy is allowed) * Serious cardiovascular disease (unstable angina, supraventricular arrhythmia, myocardial infarction, symptomatic congestive heart failure, cardiac arrhythmia, coronary artery bypass surgery within 6 months prior to registration). * Hypotension (\<90/50mm Hg), or uncontrolled hypertension (\>170/100 mm Hg) * Stroke or spinal cord injury within 6 months before registration. * Patients on Persantine, heparin, Lovenox, warfarin, ginkgo biloba, Plavix, Disalcid, other blood-thinning medication or with a history of bleeding disorders will be excluded.(Aspirin \< 325mg allowed) * Current use of cimetidine, ketoconazole, itraconazole, erythromycin, or ritonavir. Major medical or psychiatric illness which, in the opinion of the investigator, would prevent completion of treatment or would interfere with follow-up. * Current or prior use of any organic nitrate within the last 6 months (e.g., use of nitroglycerin) * May not receive other investigational agents or devices during 30 days prior to start of study drug. * History of allergic reactions attributed to compounds of similar chemical or biologic composition to ArginMax (l-arginine, ginseng, or ginkgo biloba)