Risks associated with injection therapy including bleeding, pain with injection, penile pain, priapism, and corporal fibrosis (scarring inside of the corpora cavernosa). There is also concern that repetitive injections in the same area could cause scar tissue to build up in the tunica albuginea that could create penile curvature. Thus, doctors recommended that one alternate sides with injection and perform injections no more frequent than every other day.
A variety of lifestyle choices can affect the ability to achieve and maintain an erection, so preventing ED is possible in some cases. Men are encouraged to manage chronic health problems with their doctors and to exercise regularly. They also should avoid smoking and excess alcohol and get help for anxiety or depression, according to the Mayo Clinic.
Psychological factors — Psychological issues such as depression, anxiety, guilt or fear can sometimes cause sexual problems. At one time, these factors were thought to be the major cause of impotence. Doctors now know that physical factors cause impotence in most men with the problem. However, embarrassment or "performance anxiety" can make a physical problem worse.
In a randomized double-blind, parallel, placebo-controlled trial, sildenafil plus testosterone was not superior to sildenafil plus placebo in improving erectile function in men with ED and low testosterone levels.  The objective of the study was to determine whether the addition of testosterone to sildenafil therapy improves erectile response in men with ED and low testosterone levels.
A number of herbs have been promoted for treating impotence. The most widely touted herbs for this purpose are Coryanthe yohimbe (available by prescription as yohimbine, with the trade name Yocon) and gingko (Gingko biloba), although neither has been conclusively shown to help the condition in controlled studies. In addition, gingko carries some risk of abnormal blood clotting and should be avoided by men taking blood thinners such as coumadin. Other herbs promoted for treating impotence include true unicorn root (Aletrius farinosa), saw palmetto (Serenoa repens), ginseng (Panax ginseng), and Siberian ginseng (Eleuthrococcus senticosus). Strychnos Nux vomica has been recommended, especially when impotence is caused by excessive alcohol, cigarettes, or dietary indiscretions, but it can be very toxic if taken improperly, so it should be used only under the strict supervision of a physician trained in its use.
VED involved placing the penis in a clear plastic tube where negative pressure created by the vacuum pump leads to penile engorgement and tumescence. Usually a constriction ring can be placed on the base of penis following penile engorgement. Some men complain of bruising, a “cold” penis and pain associated with the constriction ring; however, in some men with NED sensation may not be intact mitigating the side effects of VEDs. VEDs have reported effectiveness up to 90% in certain ED populations and it remains a non-invasive means to achieve and erection.
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.
Herbal supplements such as ginkgo biloba, saw palmetto, and yohimbe have been touted as sexual enhancers, and some men have been tempted to try them to treat erectile dysfunction. Bennett warns, however, that none has been approved by the FDA or even shown by any reliable studies to prevent, treat, or improve erectile dysfunction. Moreover, supplements are unregulated and can have many side effects or interfere with prescribed medications you’re already taking. Don’t jeopardize your health by taking a supplement to treat erectile dysfunction without first talking with your doctor.
Iatrogenic hypotension can occur in men in neurodegenerative disease using sildenafil (49). Hussain et al. placed men with PD and MSA on sildenafil and recorded blood pressure before and after. Half of the 12 MSA patients developed postural hypotension, while none of the twelve PD patients did. Since MSA can be difficult to distinguished diagnostically from PD, baseline blood pressure measurements prior to prescribing the medication and seeking medical assistance if symptomatic hypotension occurred was recommended for all patients with PD, and MSA. Of note, none of the men with MSA who developed hypotension discontinued sildenafil use due to its effectiveness at improving their erections.
I would think the 25% is just an average. Some men never have a problem with erections. Some healthy men in their 60's never have a problem with their erections -- no Viagra needed at all, thank you. And, no, it is NOT completely associated with age. In fact, many men in their 40's and even younger, are already dealing with ED, especially if they smoke, are obese, don't exercise, or are addicted to porn, among other things. In fact, even men in their 20's and 30's can have these problems.
Modern drug therapy for ED made a significant advance in 1983, when British physiologist Giles Brindley dropped his trousers and demonstrated to a shocked Urodynamics Society audience his papaverine-induced erection. The drug Brindley injected into his penis was a non-specific vasodilator, an alpha-blocking agent, and the mechanism of action was clearly corporal smooth muscle relaxation. The effect that Brindley discovered established the fundamentals for the later development of specific, safe, and orally effective drug therapies.[better source needed][better source needed]
Radical prostatectomy for the treatment of prostate cancer poses a significant risk of ED. A number of factors are associated with the chance of preserving erectile function. If both nerves that course on the lateral edges of the prostate can be saved, the chance of maintaining erectile function is reasonable. The odds depend on the age of the patient. Men younger than 60 years have a 75-80% chance of preserving potency, but men older than 70 years have only a 10-15% chance.
Vacuum devices: Specially designed vacuum devices to produce erections have been used successfully for many years. They are safe and relatively inexpensive. They work by creating a vacuum around the penis that draws blood into the penis, engorging it, and expanding it. There are three components to the device, a plastic cylinder in which the penis is placed, a battery or hand operated pump that draws air out of the cylinder creating the vacuum, and an elastic band (constriction device) that is placed around the base of the penis, to maintain the erection after the cylinder is removed and during intercourse by preventing blood from flowing out of the penis back into the body.
Men with a rare heart condition known as long QT syndrome should not take vardenafil since this may lead to abnormal heart rhythms. The QT interval is the time it takes for the heart's muscle to recover after it has contracted. An electrocardiogram (EKG) measures the QT interval. Some people have longer than normal QT intervals, and they may develop potentially life-threatening abnormal heart rhythms, especially when given certain medications. Men with a family history of long QT syndrome should not take vardenafil, as it is possible to inherit long QT syndrome. Furthermore, vardenafil is not recommended for men who are taking medications that can affect the QT interval such as quinidine (Quinaglute, Quinidex), procainamide (Pronestyl, Procan-SR, Procanbid), amiodarone (Cordarone), and sotalol (Betapace).
Ginseng, specifically “red ginseng,” is known as the “herbal Viagra” that helps puts to rest men’s bedroom woes. Red ginseng is when the root has been steamed and then dried. The ginseng root is the part of the plant that is mostly used as a natural remedy when in its supplement form. However, the plant must be grown for a minimum of five years before it can be used. In a 2008 review, seven studies on red ginseng and ED, ranging in dosages from 600 to 1,000 milligrams three times a day, were found to provide evidence for the effectiveness of the herb in ED treatment.
There have been rare reports of priapism (prolonged and painful erections lasting six or more hours) with the use of PDE5 inhibitors. Patients with blood cell diseases such as sickle cell anemia, leukemia, and multiple myeloma have higher than normal risks of developing priapism. Untreated priapism can cause injury to the penis and lead to permanent impotence. Therefore, if your erection lasts four hours, you should seek emergency care.
What happens is that the blood vessels of the penis are rather small, and a small amount of plaque in the penile arteries is going to result in erectile dysfunction. You need more plaque before the person’s actually symptomatic from a heart problem, but they’re linked. And so when anybody, any man has an erectile issue, it’s incumbent upon the physician to make certain that their cardiac status is healthy.
It is normal for a man to have five to six erections during sleep, especially during rapid eye movement (REM). Their absence may indicate a problem with nerve function or blood supply in the penis. There are two methods for measuring changes in penile rigidity and circumference during nocturnal erection: snap gauge and strain gauge. A significant proportion of men who have no sexual dysfunction nonetheless do not have regular nocturnal erections.
Research is mixed on the effectiveness of acupuncture as an erectile dysfunction cure, but one study published in November 2013 in the Journal of Alternative and Complementary Medicine found that acupuncture can be beneficial for men experiencing erectile dysfunction as a side effect of antidepressants, including selective serotonin reuptake inhibitors (SSRIs) and serotonin noradrenaline reuptake inhibitors (SNRIs).
Achieving an erection is a complicated process, requiring transmission of sensations from the genital area to the nervous system and the return of nervous impulses to the muscles and blood vessels of the penis. Anything that interferes with this interchange, such as disease or injury of the blood vessels, muscles, or nerves, can make achieving and maintaining an erection difficult. Psychological factors, such as anxiety and depression, can also interfere with erectile function. Anxiety and depression may also develop as a consequence of impotence.
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). 
In a prospective, multicenter, single-armed study of ED patients who exhibited a suboptimal response to PDE5 inhibitors, the investigators found that percutaneous implantation of zotarolimus-eluting stents in focal atherosclerotic lesions was both safe and feasible and was associated with clinically meaningful improvement on subjective and objective measures of erectile function. 
Soler et al. compared sildenafil to vardenafil and tadalafil (69). Sildenafil was effective in 85% of SCI patients, 74% of the patients on vardenafil and 72% of the patients on tadalafil. Sildenafil was associated with more rigid and longer lasting erections. Additionally, 50 mg of sildenafil was effective in 55% of patients compared to more than 70% of the patients on vardenafil and tadalafil requiring 20 mg for a similar response. Men who used tadalafil were able to achieve erections 24 hours after administration, improving overall satisfaction related to the possible spontaneity of sexual encounters. Del Popolo also evaluated the time/duration effectiveness of PDE5i sildenafil 50 mg versus tadalafil 10 mg (64). Tadalafil 10 mg significantly increased the percentage of successful intercourse attempts at 12–24 hours compared with sildenafil. One can suspect that vardenafil, which has a longer half-life than sildenafil, could offer a similar benefit but a study investigating this occurrence has yet to be performed.
Usually there will not be a specific treatment that will lead to the improvement of erectile dysfunction. However, there are treatments that will allow erections to happen and can be used to allow sexual activity to take place. There are three main types of treatments: non-invasive treatments such as tablet medicines and external devices (e.g. vacuum device); penile injections; or for men who have not had success with other treatments, surgery may be an option.