Erectile dysfunction (ED) is the inability of a man to achieve or maintain an erection sufficient for his sexual needs or the needs of his partner. Most men experience this at some point in their lives, usually by age 40, and are not psychologically affected by it.
Some men, however,
experience chronic, complete erectile dysfunction (impotence), and others,
partial or brief erections. Frequent erectile dysfunction can cause
emotional and relationship problems, and often leads to diminished self-esteem.
Erectile dysfunction has many causes, most of which are treatable, and
is not an inevitable consequence of aging.
The term "erectile dysfunction" can mean the inability to achieve erection, an inconsistent ability to do so, or the ability to achieve only brief erections. These various definitions make estimating the incidence of erectile dysfunction difficult. According to the National Institutes of Health in 2002, an estimated 15 million to 30 million men in the United States experience chronic erectile dysfunction.
According to the National Ambulatory Medical Care Survey (NAMCS), approximately 22 out of every 1000 men in the United States sought medical attention for ED in 1999.
Incidence of the disorder increases with age. Chronic ED affects about 5% of men in their 40s and 15–25% of men by the age of 65. Transient ED and inadequate erection affect as many as 50% of men between the ages of 40 and 70.
Diseases (e.g., diabetes, kidney disease, alcoholism, atherosclerosis) account for as many as 70% of chronic ED cases and psychological factors (e.g., stress, anxiety, depression) may account for 10–20% of cases. Between 35 and 50% of men with diabetes experience ED.
The internal structure of the penis consists of two cylinder-shaped vascular tissue bodies (corpora cavernosa) that run throughout the penis; the urethra (tube for expelling urine and ejaculate); erectile tissue surrounding the urethra; two main arteries; and several veins and nerves. The longest part of the penis is the shaft, at the end of which is the head, or glans penis. The opening at the tip of the glans, which allows for urination and ejaculation, is the meatus.
The physiological process of erection begins in the brain and involves the nervous and vascular systems. Neurotransmitters in the brain (e.g., epinephrine, acetylcholine, nitric oxide) are some of the chemicals that initiate it. Physical or psychological stimulation (arousal) causes nerves to send messages to the vascular system, which results in significant blood flow to the penis. Two arteries in the penis supply blood to erectile tissue and the corpora cavernosa, which become engorged and expand as a result of increased blood flow and pressure.
Because blood must stay in the penis to maintain rigidity, erectile tissue is enclosed by fibrous elastic sheathes (tunicae) that cinch to prevent blood from leaving the penis during erection. When stimulation ends, or following ejaculation, pressure in the penis decreases, blood is released, and the penis resumes its normal shape.
There are many underlying physical and psychological causes of erectile dysfunction. Reduced blood flow to the penis and nerve damage are the most common physical causes. Underlying consitions associated with erectile dysfunction include the following:
Risk factors for arteriosclerosis include:
Smoking, which can lead to any of the above risk factors, is perhaps the most significant risk factor for impotence related to arteriosclerosis.
Surgery, Radiation Therapy
New nerve-sparing techniques aimed at lowering the incidence of impotence to 40% to 60% are now being developed and used in these surgeries. Temporary impotence is also associated with these procedures, even those in which nerve-sparing techniques were used. It can take as long as 6 to 18 months for full erections to return.
Radical cystectomy (for bladder cancer) and prostatectomy (for prostate cancer) require cutting or removing nerves that control penile blood flow. These nerves do not control sensation in the penis and are not responsible for orgasms; only erection is affected by these procedures.
Radiation therapy for prostate or bladder cancer also can permanently damage these nerves.
A significant number of men develop impotence from psychological causes that can be overcome. When a physiological cause is treated, subsequent self-esteem problems may continue to impair normal function and performance. Qualified therapists (e.g., sex counselors, psychotherapists) work with couples to reduce tension, improve sexual communication, and create realistic expectations for sex, all of which can improve erectile function.
Psychological therapy may be effective in conjunction with medical or surgical treatment. Sex therapists emphasize the need for men and their partners to be motivated and willing to adapt to psychological and behavioral modifications, including those that result from medical or surgical treatment.
Selective enzyme inhibitors are available by prescription and may be taken up to once a day to treat ED. They improve partial erections by inhibiting the enzyme that facilitates their reduction and increase levels of cyclic guanosine monophosphate (cGMP, a chemical factor in metabolism), which causes the smooth muscles of the penis to relax, enabling blood to flow into the corpora cavernosa.
Patients taking nitrate drugs (used to treat chest pain) and those taking alpha-blockers (used to treat high blood pressure and benign prostatic hyperplasia should not take selective enzyme inhibitors.
Men who have had a heart attack or stroke within the past 6 months and those with certain medical conditions (e.g., uncontrolled high blood pressure, severe low blood pressure or liver disease, unstable angina) that make sexual activity inadvisable should not take Cialis®. Dosages of the drug should be limited in patients with kidney or liver disorders.
Viagra® is absorbed and processed rapidly by the body and is usually taken 30 minutes to 1 hour before intercourse. Results vary depending on the cause of erectile dysfunction, but studies have shown that Viagra is effective in 75% of cases. It helps men with erectile dysfunction associated with diabetes mellitus (57%), spinal cord injuries (83%), and radical prostatectomy (43%).
In clinical studies, Levitra® has been shown to work quickly, provide consistent results, and improve sexual function in most men the first time they take the drug. It also has shown to be effective in men of all ages, in patients with diabetes mellitus, and in men who have undergone radical prostatectomy.
Cialis® has been shown in clinical trials to stay in the body longer than the other selective enzyme inhibitors. It promotes erection within 30 minutes and enhances the ability to achieve erection for up to 36 hours.
Common side effects of selective enzyme inhibitors include headache, reddening of the face and neck (flushing), indigestion, and nasal congestion. Cialis® may cause muscle aches and back pain, which usually resolve on their own within 48 hours.
Yohimbine improves erections for a small percentage of men. It stimulates the parasympathetic nervous system, which is linked to erection, and may increase libido. It is necessary to take the medication for 6 to 8 weeks before determining whether it will work or not.
Yohimbine has a stimulatory effect and side effects include elevated heart rate and blood pressure, mild dizziness, nervousness, and irritability. Yohimbine's effects have not been studied thoroughly, but some studies suggest that 10% to 20% of men respond to treatment with the drug.
Ease of administration makes oral medication advantageous. Some drugs, however, are suitable for only a relatively small group of men, and in many cases, oral medications may by less effective than other treatments.
These drugs have been shown to produce erections in 80% of men who inject them. Some men claim that they produce erections that feel natural and improve sex. The injections are relatively painless and create an erection that begins about 5 to 15 minutes after the injection. It is recommended that self-injection be performed no more than once every 4 to 7 days. Side effects include infection, bleeding, and bruising at the injection site, dizziness, heart palpitations, and flushing. There is a small risk for priapism (an erection that lasts for more than 6 hours and requires medical relief). Repeated injection may cause scarring of erectile tissue, which can further impair erection.
Urethral suppositories containing prostaglandin (aprostadil), like Muse® (Medicated Urethral System for Erections), may be an alternative to injection. Using a hand-held delivery device, a man inserts a prostaglandin pellet through the meatus (penis opening) into the urethra. Prostaglandin is absorbed through the urethral mucosa and into the surrounding erectile tissue. It is available with a prescription, is well tolerated, and may improve erections in 60% of men who use it.
In addition to the side effects associated with injecting aprostadil, pain in the penis and perineum (area between scrotum and rectum) may occur with suppository use.
Vacuum devices work best in men who are able to achieve partial erections on their own. They are easy to use at home, require no other procedure, and typically improve erections regardless of the cause of impotence. Some men experience a numbing feeling after placing the O-ring. Since the penis is flaccid between the ring and the body, the erection may be somewhat floppy.
Penile implants involve surgical insertion of malleable or inflatable rods or tubes into the penis. A semi-rigid prosthesis is a silicon-covered flexible metal rod. Once inserted, it provides the rigidity necessary for intercourse and can be curved slightly for concealment. It requires the simplest surgical procedure of all the prostheses. Its main disadvantage is that concealment can be difficult with certain types of clothing.
An inflatable penile prosthesis consists of two soft silicone or bioflex (plastic) tubes inserted in the penis, a small reservoir implanted in the abdomen, and a small pump implanted in the scrotum. To produce an erection, a man pumps sterile liquid from the reservoir into the tubes by squeezing the pump in the scrotum. The tubes act as erectile tissue and expand to form an erection. When the erection is no longer desired, a valve allows the fluid to return to the reservoir. Inflatable prostheses are the most natural feeling of the penile implants and they allow for control of rigidity and size.
The surgical procedure to implant the inflatable prosthesis is slightly more complicated than for a semi-rigid implant. Also, because there are more mechanical parts, there is a higher risk for mechanical failure requiring repair or adjustment.
A self-contained inflatable prosthesis is similar but has fewer parts. It consists of a pair of inflatable tubes in the penis with a pump attached directly to the end of the implant. The reservoir is also located in the shaft of the penis. Its compact design allows for simpler implantation, but because it takes up more space in the penis, there is less room for expansion.
Types of Penile Implants
Venous ligation is performed to prevent venous leak. Problematic veins are bound (ligated) or removed, which allows an adequate amount of blood to remain in the penis. It may improve function in 40% to 50% of men, but some men may experience problems over the long term.
Vascular surgery for erectile dysfunction is rarely performed and is generally considered experimental. Risks include nerve damage and the creation of scar tissue, both of which are causes of impotence. Surgeons experienced with these procedures may be difficult to find.