Exercise and lifestyle modifications may improve erectile function. Weight loss may help by decreasing inflammation, increasing testosterone, and improving self-esteem. Patients should be educated to increase activity, reduce weight, and stop smoking, as these efforts can improve or restore erectile function in men without comorbidities. Precise glycemic control in diabetic patients and pharmacologic treatment of hypertension may be important in preventing or reducing sexual dysfunction. 
Injection therapy involves injecting a substance into the penis to enhance blood flow and cause an erection. The Food and Drug Administration (FDA) approved a drug called alprostadil (Caverject) for this purpose in July of 1995. Alprostadil relaxes smooth muscle tissue to enhance blood flow into the penis. It must be injected shortly before intercourse. Another, similar drug that is sometimes used is papaverine—not yet been approved by the FDA for this use. Either drug may sometimes cause painful erections or priapism (uncomfortable, prolonged erections) that must be treated with a shot of epinephrine.
Cavallini, G., Modenini, F., Vitali, G., & Koverech, A. (2005, November). Acetyl-L-carnitine plus propionyl-L-carnitine improve efficacy of sildenafil in treatment of erectile dysfunction after bilateral nerve-sparing radical retropubic prostatectomy. Urology, 66(5), 1080-5. Retrieved from http://www.sciencedirect.com/science/article/pii/S0090429505006515
Clearly, PDE5i have revolutionized the treatment of ED in general and the neurogenic ED population is no exception. They remain safe and effective in most men with neurogenic ED; however, care must be taken in prescribing PDE5i to men high spinal cord lesions, MSA or possibly PD. VEDs are minimally-invasive and can be as effective as other modalities at leading to erection. However, high discontinuation rates are associated with VED use related to pain, difficulty using the device or cold penis. Intracavernosal therapy has been a mainstay of treatment for neurogenic ED and remains extremely successful in the SCI population. Trial of intracavernosal therapy for other causes of neurogenic ED can be considered second-line therapy, but there is a relative paucity of data for clinical outcomes related to its use outside of SCI men. Surgical therapy via penile implantation remains another second line approach and may also be utilized to assist men with bladder management. Higher complication rates of infections, and perforation have been reported compared to neurologically intact men. Many other compounds are currently being evaluated for the treatment of neurogenic ED as well as gene and stem cell therapy, but still should be considered investigational until substantiated by randomized controlled trials.
There are many different treatment options for erectile dysfunction but your individual diagnosis will determine which treatment option is right for you. It is important to realize that not all treatment options will work for everyone. A doctor who has specialized in men’s sexual health (typically a urologist) will be the most qualified to discuss all of your treatment options with you. Many specialists will often encourage you to schedule additional follow up appointments to review how your treatment is working for you or if a different option may be more beneficial.
PDE5i for ED in patients with MS can be considered as reasonably effective and safe. Fowler et al. performed a randomized, multicenter, double-blind, flexible dose trial with open label extensions comparing sildenafil to placebo (75). A nearly 4-fold increase in effective erections was noted in the treatment arm, 96% vs. 24%. Sexual satisfaction and overall satisfaction were also improved in the treatment group based on IIEF scores, and quality of life assessments. Lombardi et al. evaluated tadalafil use in men with MS (71). Seventy eight percent of the men responded with improved erections, better quality of life with regards to sexual function, partner relationship and family life. Just less than half the men who responded to the tadalafil did so at the lower dosage of 10 mg. Subjects in either studies did not have any significant adverse side effects beyond flushing, and headache with PDE5i use.
For best results, men with ED take these pills about an hour or two before having sex. The drugs require normal nerve function to the penis. PDE5 inhibitors improve on normal erectile responses helping blood flow into the penis. Use these drugs as directed. About 7 out of 10 men do well and have better erections. Response rates are lower for Diabetics and cancer patients.