Injections: Injections are a reliable way to restore testosterone levels, but this therapy requires periodic injections (usually every two weeks) to sustain an effective level. It also causes high hormone levels right after the injection and low hormone levels just before the next shot. This is thought to be slightly more risky than other methods that maintain a moderate hormone level throughout the treatment period.
These are not currently approved by the FDA for ED management, but they may be offered through research studies (clinical trials). Patients who are interested should discuss the risks and benefits (informed consent) of each, as well as costs before starting any clinical trials. Most therapies not approved by the FDA are not covered by government or private insurance benefits.
Talk with your doctor before trying supplements for ED. They can contain 10 or more ingredients and may complicate other health conditions. Asian ginseng and ginkgo biloba (seen here) are popular, but there isn't a lot of good research on their effectiveness. Some men find that taking a DHEA supplement improves their ability to have an erection. Unfortunately, the long-term safety of DHEA supplements is unknown. Most doctors do not recommend using it.
Think of erectile dysfunction as your body’s “check engine light.” The blood vessels in the penis are smaller than other parts of the body, so underlying conditions like blocked arteries, heart disease, or high blood pressure usually show up as ED before something more serious like a heart attack or stroke. ED is your body’s way of saying, “Something is wrong.” And the list of things that cause erectile dysfunction can include:
One study by Palmer and colleagues evaluated sildenafil use in SB males with thoracic lesions (76). A prospective, blinded, randomized, placebo-controlled, dose-escalation, crossover study in 17 patients with SB and ED was performed. All study participates took sets of tablet in groups, two sets of placebo, one of 25 mg, and the last 50 mg. Overall response to the tablet sets was measured by IIEF response and self-report of erectile rigidity. Patients reported that taking 50 mg of sildenafil led to improved erections, duration of erections, frequency of erections and level of confidence compared to sildenafil 25 mg and more significantly compared to placebo. Of the five patients who reported side effects, two experienced mild hematological changes that reverted to baseline after study completion.
In one study, 9.6% reported ‘occasional’ erectile dysfunction, 8.9% reported erectile dysfunction occurring ‘often’, and 18.6% reported erectile dysfunction occurring ‘all the time’. Of these, only 11.6% had received treatment.In another study, only 14.1% of men reported that they had received treatment, despite experiencing erectile dysfunction for longer than 12 months.
Zerman et al. performed penile implant surgery in 245 men with neurolgic impairment caused by spinal cord injury, CNS neoplasm, CNS infection, MS and SB (110). Mean follow-up time of 7.2 years was achieved in 195 patients, 50 patients were excluded for lost to follow-up or death from nonurological causes. Interestingly, 135 patients underwent penile implantation to assist with management of urinary incontinence and improve ability for condom/intermittent catheterization. Ninety-two patients patient underwent implantation for ED. Eighty two percent of patients were satisfied with implantation for ED, and 67% of partners were satisfied. Complications included infection (5%), perforation (0–18%), and technical dysfunction (7–33%). Perforation rates were high with the malleable device when it was placed through a subcoronal incision. After adopting an infrapubic approach the perforation rates dropped substantially.
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
For obvious reasons, ED can be a sensitive subject, one that until relatively recently men were more likely to try to hide than to deal with. Fortunately, a deeper understanding of the variety of causes of erectile dysfunction has led to medications, therapies, and other treatments that can be more individualized and more likely to be effective—and more open discussion about addressing the concern.
Vascular damage may result from radiation therapy to the pelvis and prostate in the treatment of prostate cancer.  Both the blood vessels and the nerves to the penis may be affected. Radiation damage to the crura of the penis, which are highly susceptible to radiation damage, can induce ED. Data indicate that 50% of men undergoing radiation therapy lose erectile function within 5 years after completing therapy; fortunately, some respond to one of the PDE5 inhibitors.
The role of the endothelium in erectile function became clearer with the observation that the phosphodiesterase type 5 (PDE5) inhibitor, sildenafil, enhanced erectile function. Erection occurs with the release of nitric oxide (NO) from the vascular endothelial cells.17 The reduction in endothelial cell production of NO results in the negative impact on the smooth muscles in the corporal bodies and results in less relaxation of the smooth muscle cells with decrease in blood supply and resulting ED. A similar phenomenon is well known to impact the coronary arterial system resulting in CVD.
Both ED and low testosterone (hypogonadism) increase with age. The incidence of the latter is 40% in men aged 45 years and older.  Testosterone is known to be important in mood, cognition, vitality, bone health, and muscle and fat composition. It also plays a key role in sexual dysfunction (eg, low libido, poor erection quality, ejaculatory or orgasmic dysfunction, reduced spontaneous erections, or reduced sexual activity). 
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In comparison, 37% of men who had received external radiotherapy as their primary therapy reported the ability to attain functional erections suitable for intercourse, along with 43% of men who had received brachytherapy as primary treatment. Pretreatment sexual health-related quality of life score, age, serum prostate-specific antigen (PSA) level, race or ethnicity, body mass index, and intended treatment details were associated with functional erections 2 years after treatment. 
Supplements are popular and often cheaper than prescription drugs for ED. However, supplements have not been tested to see how well they work or if they are a safe treatment for ED. Patients should know that many over-the-counter drugs have been found on drug testing to have ‘bootlegged' PDE 5 Inhibitors as their main ingredient. The amounts of Viagra, Cialis, Levitra or Stendra that may be in these supplements is not under quality control and may differ from pill to pill. The FDA has issued consumer warnings and alerts.