Definition
Erectile dysfunction (ED), formerly known as
impotence,
is
the inability to
achieve or
maintain an
erection long enough to
engage in
sexual intercourse.
Description
Under normal circumstances, when a man is sexually stimulated, his brain sends a message down the spinal cord and intothe nerves of the penis. The nerve endings in the penis release chemical messengers, called neurotransmitters, that signalthe arteries that supply blood to the corpora cavernosa (the two spongy rods of tissue that span the length of the penis) torelax and fill with blood. As they expand, the corpora cavernosa close off other veins that would normally drain blood fromthe penis. As the penis becomes engorged with blood, it enlarges and stiffens, causing an erection. Problems with bloodvessels, nerves, or tissues of the penis can interfere with an erection.
Causes and symptoms
It
is
estimated that up
to
30
million American men frequently suffer from ED
and that it
strikes up
to
half of
all men betweenthe ages of
40
and 70. Doctors used to
think that most cases of
ED
were psychological in
origin, but they now recognizethat, at
least in
older men, physical causes may play a
primary role in
60% or
more of
all cases. In
men over the age of
60,the leading cause is
atherosclerosis,
or
narrowing of
the arteries, which can restrict the flow of
blood to
the penis. Injury or
disease of
the connective tissue, such as
Peyronie's disease, may prevent the corpora cavernosa from completelyexpanding. Damage to
the nerves of
the penis from certain types of
surgery or
neurological conditions, such as
Parkinson'sdisease or
multiple sclerosis,
may also cause ED. Men with diabetes are especially at
risk for erectile dysfunctionbecause of
their high risk of
both atherosclerosis and a
nerve disease called diabetic neuropathy.
Some drugs, including certain types of
blood pressure medications, antihistamines,
tranquilizers (especially beforeintercourse), and antidepressants known as
selective serotonin reuptake inhibitors (SSRIs, including Prozac and Paxil)can interfere with erections. Smoking,
excessive alcohol consumption, and illicit drug use may also contribute. In
somecases, low levels of
the male hormone testosterone may contribute to
erectile failure. Finally, psychological factors, suchas
stress,
guilt, or
anxiety,
may also play a
role, even when the ED
is
primarily due to
organic causes.
Diagnosis
When diagnosing the underlying cause of erectile dysfunction, the doctor begins by asking the man a number of questionsabout when the problem began, whether it only happens with specific sex partners, and whether he ever wakes up with anerection. (Men whose dysfunction occurs only with certain partners or who wake up with erections are more likely to have apsychological cause for their ED.) Sometimes, the man's sex partner is also interviewed. In some cases, domestic discordmay be a factor.
The doctor also obtains a
thorough medical history to
find out about past pelvic surgery, diabetes, cardiovascular disease,kidney disease,
and any medications the man may be
taking. The physical examination should include a
genitalexamination, hormone tests, and a
glucose test for diabetes. Sometimes a
measurement of
blood flow through the penismay be
taken.
Treatment
Years ago, the standard treatment for erectile dysfunction was a penile implant or long-term psychotherapy. Althoughphysical causes are now more readily diagnosed and treated, individual or marital counseling is still an effective treatmentfor ED when emotional factors play a role.
There are three prescription medications available in
the United States to
treat the physical causes of
ED: sildenafil citrate (Viagra), vardenafil (Levitra), and tadalafil (Cialis). They help about three-fourths of
all men who try them in
thegeneral population. Several studies have indicated that their success rate in
diabetic men may be
slightly lower, averagingaround 60-65%. All three pills work by
enhancing the effects of
nitric oxide. This chemical relaxes muscles in
the penis to
allow more blood to
flow in. These pills do
not cause an
erection by
themselves. Sexual stimulation is
also required.Sildenafil or
vardenafil should be
taken about an
hour before sex. Each is
effective for roughly four hours. Tadalafil lasts forup
to
36
hours. Men should not have sex more than once every 24
hours after using these drugs. Before Viagra's approval in1998, drug treatment of
erectile dysfunction was limited to
alprostadil (prostaglandin [E.sub.1]), either injected into the penisor
inserted as
a
pellet into the urethra. Sales of
the three newer ED
drugs reached $3.4 billion in
2004, according to
theresearch firm IMS Health. In
2004, Viagra had about 66% of
the market share for ED
drugs compared to
19% for Levitra and14% for Cialis.
Viagra
Sildenafil citrate was originally developed in
1991 as
a
treatment for angina,
or
chest pain.
The drug, marketed under thename Viagra, received FDA approval as
a
treatment for erectile dysfunction in
March 1998, and since that time it
has beenprescribed for more then 20
million men worldwide. It
was the first oral medication approved for ED
treatment. Viagra is
a
vasodilator, a
drug that has the effect of
dilating the blood vessels. It
works by
improving blood circulation to
the penis, andby
enhancing the effects of
nitric oxide, the agent that relaxes the smooth muscle of
the penis and regulates blood vesselsduring sexual stimulation, allowing the penis to
become engorged and achieve an
erection.
The average recommended dose of Viagra is 50 mg. It comes in doses of 25 mg., 50 mg., and 100 mg to. The medication istaken approximately one hour before sexual activity is planned, and may remain effective for up to four hours. One drawbackis that to be effective, it should be taken on an empty stomach. Also, high-fat foods can interfere with the absorption ofViagra. Viagra does not increase sexual desire. Sexual stimulation and arousal are required for it to be effective.
Many insurance plans cover the cost of Viagra, provided it is prescribed to treat erectile dysfunction. The pills costapproximately $10 each, and insurers may limit coverage to a specific number of pills each month.
The primary drawback to
Viagra, which works about an
hour after it
is
taken, it
that the FDA cautions men with heartdisease or
low blood pressure to
be
thoroughly examined by
a
physician before obtaining a
prescription. At
least 130 menhave died while taking Viagra. However, the FDA said the men—most over the age of
64—died of
heart attack or
strokedue to
health problems exaggerated by
sexual activity, not the drug itself.
Levitra
In early 2003, a second prescription drug to treat erectile dysfunction, Levitra, was approved by the FDA. Like Viagra,Levitra helps increase blood flow to the penis and may help men with ED get and keep an erection. Once a man hascompleted sexual activity, blood flow to the penis should decrease and the erection should go away. Levitra should be takenapproximately 60 minutes prior to sexual activity. In clinical trials, most patients were able to begin sexual activity beforethat time. A 2004 study showed that about 50% of men taking Levitra experienced a firm erection within 25 minutes and asmall percentage in as quickly as 10 minutes. Studies also showed that Levitra improved erectile function in men who hadother health factors, such as diabetes or prostate surgery.
Men taking nitrate drugs, often used to control chest pain (also known as angina), should not take Levitra. Men who usealpha-blockers, sometimes prescribed for high blood pressure or prostate problems, also should not take Levitra. Suchcombinations could cause blood pressure to drop to an unsafe level. Levitra is available in 2.5 mg, 5 mg, 10 mg, and 20 mgtablets and should be taken no more than once a day. The average cost per pill is about $10 and is covered by manyinsurance plans.
Cialis
Cialis is the third oral drug prescribed to treat erectile dysfunction, approved by the FDA in November 2003. Its most notabledifference from Viagra and Levitra, which work for about four hours, is that Cialis works for up to 36 hours. Cialis helpsincrease blood flow in the penis when a man is sexually stimulated. It can help men with ED get and keep an erectionsatisfactory for sexual activity. Once a man has completed sexual activity, blood flow to his penis decreases, and hiserection goes away. Cialis is clinically proven to improve erectile function in most men with ED, including those with mild,moderate or severe ED.
The most common side effects with Cialis are headache,
upset stomach, back pain, and muscle aches. These sideeffects usually go
away after a
few hours. Patients who get back pain and muscle aches usually get it
12
to
24
hours aftertaking Cialis. Back pain and muscle aches usually go
away by
themselves within 48
hours.
Cialis comes in 5 mg., 10 mg. (the recommended starting dose), and 20 mg. tablets. The average cost per tablet is about$10 and it is covered by many insurance plans. Since the absorption of Cialis is not affected by food or high-fat foods, itdoes not need to be taken on an empty stomach. Studies show that in most men, Cialis begins working in about 30minutes and may be taken up to once per day by most patients.
Priapism,
a
prolonged erection, is
a
very rare potential side effect of
all prescription ED
medications. Persons takingViagra, Levitra, or
Cialis who have a
prolonged erection, lasting more than four hours, should seek immediate medicalattention. Priapism can cause damage to
the penis potentially leading to
the permanent inability to
have an
erection.
Because sexual activity can stress the heart, men who have heart problems should check with their physician to
see if
sexual activity is
recommended. Erectile dysfunction drugs may trigger temporary hypotension (low blood pressure) and is
known to
increase cardiovascular nerve activity, so
physicians should prescribe them with caution in
men with a
history of
heart attack, atherosclerosis (hardening of
the arteries), angina, arrhythmia, and chronic low blood pressure problems. ED
drugs are not labeled or
approved for use by
women or
children, or
by
men without erectile dysfunction. Anyoneexperiencing cardiovascular symptoms such as
dizziness,
chest or
arm pain, and nausea when participating in
sexualactivity after taking an
ED
medication should stop the encounter. They should also not take any ED
drug again until theyhave discussed the episode with their healthcare provider. It
is
recommended that men with kidney or
liver impairments, andmen over age 65, start at
the lowest possible dosage of
ED
medications.
Other treatment options
Although the commercial availability of
Viagra, Levitra, and Cialis has been useful in
many men, prostate cancer patientsand ED
caused by
psychological problems often require alternative treatment. A
commonly used alternative consists of
a
three-drug injection containing alprostadil, papaverine hydrochloride, and phentolamine mesylate. Though it
is
commonlyreferred to
as
the "Knoxville formula," apparently for the city of
its original introduction, a
number of
slightly varying formulashave been in
use around the country. The three-drug preparation is
administered by
injection into the corpora cavernosa to
induce erection.
Other traditional therapies for ED include vacuum pump therapy, injection therapy involving injecting a substance into thepenis to enhance blood flow, and a penile implantation device. In rare cases, if narrowed or diseased veins are responsiblefor ED, surgeons may reroute the blood flow into the corpora cavernosa or remove leaking vessels.
In vacuum pump therapy, a man inserts his penis into a clear plastic cylinder and uses a pump to force air out of thecylinder. This forms a partial vacuum around the penis, which helps to draw blood into the corpora cavernosa. The man thenplaces a special ring over the base of the penis to trap the blood inside it. The only side effect with this type of treatment isoccasional bruising if the vacuum is left on too long.
Injection therapy involves injecting a substance into the penis to enhance blood flow and cause an erection. The FDAapproved a drug called alprostadil (Caverject) for this purpose in 1995. Alprostadil relaxes smooth muscle tissue to enhanceblood flow into the penis. It must be injected shortly before intercourse. Another, similar drug that is sometimes used ispapaverine. Either drug may sometimes cause painful erections or priapism that must be treated with a shot of epinephrine.Alprostadil may also be administered into the urethral opening of the penis. In MUSE (medical urethral system for erection),the man inserts a thin tube the width of a spaghetti noodle into his urethral opening and presses down on a plunger todeliver a tiny pellet containing alprostadil into his penis. The drug takes about 10 minutes to work and the erection lastsabout an hour. The main side effect is a sensation of pain and burning in the urethra, which can last about five to 15minutes. The injection process itself is often painful
Implantable penile prostheses are usually considered a
last resort for treating erectile dysfunction. They are implanted in
the corpora cavernosa to
make the penis rigid without the need for blood flow. The semi-rigid type of
prosthesis consists ofa
pair of
flexible silicone rods that can be
bent up
or
down. This type of
device has a
low failure rate but, unfortunately, it
causes the penis to
always be
erect, which can be
difficult to
conceal under clothing.
The inflatable type of device consists of cylinders that are implanted in the corpora cavernosa, a fluid reservoir implanted inthe abdomen, and a pump placed in the scrotum. The man squeezes the pump to move fluid into the cylinders and causethem to become rigid. (He reverses the process by squeezing the pump again.) While these devices allow for intermittenterections, they have a slightly higher malfunction rate than the silicon rods. Men can return to sexual activity six to eightweeks after implantation surgery. Since implants affect the corpora cavernosa, they permanently take away a man's abilityto have a natural erection.
Alternative treatment
A number of herbs have been promoted for treating erectile dysfunction. The most widely touted is yohimbe (Corynantheyohimbe), derived from the bark of the yohimbe tree native to West Africa. It has been used in Europe for about 75 years totreat ED. The FDA approved yohimbe as a treatment for ED in the late 1980s. It is sold as an over-the-counter dietarysupplement and as a prescription drug under brand names such as Yocon, Aphrodyne, Erex, Yohimex, Testomar,Yohimbe, and Yovital.
There is no clear medical research that indicates exactly how or why yohimbe works in treating ED. It is generally believedthat yohimbe dilates blood vessels and stimulates blood flow to the penis, causing an erection. It also prevents blood fromflowing out of the penis during an erection. It may also act on the central nervous system, specifically the lower spinal cordarea where sexual signals are transmitted. Studies show it is effective to some degree in 30-40% of men with ED. It isprimarily effective in men with ED caused by vascular, psychogenic (originating in the mind), or diabetic problems. It usuallydoes not work in men whose dysfunction is caused by organic nerve damage. In healthy men without ED, yohimbe in somecases appears to increase sexual stamina and prolong erections. The usual dosage of yohimbine (yohimbe extract) to treatED is 5.4 mg three times a day. It may take three to six weeks for it to take effect.
Ginkgo Ginkgo biloba,
is
also used to
treat erectile dysfunction, although it
has not been shown to
help the condition in
controlled studies, and probably has more of
a
psychological effect. In
addition, ginkgo carries some risk of
abnormal bloodclotting and should be
avoided by
men taking blood thinners, such as
coumadin. Other herbs promoted for treating ED
include true unicorn root Aletrius farinosa,
saw palmetto Serenoa repens,
ginseng Panax ginseng,
and Siberian ginsengEleuthrococcus senticosus.
Nux vomica Strychnos nux-vomica has been recommended, especially when ED
is
caused by
excessive alcohol, cigarettes, or
dietary indiscretions. Nux vomica can be
very toxic if
taken improperly, so
it
should be
used only under the strict supervision of
a
physician trained in
its use.
There are quite a
few Chinese herbal remedies for erectile dysfunction usually combinations of
herbs and sometimes animalparts such as
deer antler and sea horse. Acupuncture is
also used to
treat ED, although Western doctors question itseffectiveness.
Key terms
Angina —
A
condition in
which lack of
blood to
the heart causes severe chest pain.
Antihistamines —
A
drug that blocks cell receptors for histamine, usually to
prevent allergic effects such as
sneezing anditching.
Arrhythmia —
An
irregularity in
the normal rhythm or
force of
the heartbeat.
Atherosclerosis —
An
arterial disease in
which raised areas of
degeneration and cholesterol deposits (plaques) form on
theinner surfaces of
the arteries. Also called hardening of
the arteries.
Corpora cavernosa —
Either of
a
pair of
columns of
erectile tissue at
either side of
the penis that, together with the corpusspongiosum, produce an
erection when filled with blood.
Diabetic neuropathy —
A
disease or
disorder, especially a
degenerative one, caused by
diabetes that affects the nervoussystem.
Neurotransmitter —
A
chemical that carries messages between different nerve cells or
between nerve cells and muscles.
Peyronie's disease —
Local fibrous scarring causing the erect penis to
be
bent to
such a
degree that it
interferes withsexual intercourse.
Priapism —
A
prolonged erection lasting more than four hours.
SSRIs —
Selective serotonin reuptake inhibitors, a
class of
medication used to
treat depression.
Vasodilator —
An
agent, such as
a
nerve or
hormone, that widens the blood vessels, which in
turn decreases resistanceto
blood flow and lowers blood pressure.
Prognosis
With proper diagnosis, erectile dysfunction can nearly always be treated or coped with successfully. Unfortunately, fewerthan 10% of men with ED seek treatment. However, with the heavy advertising and marketing associated with Viagra,Levitra, and Cialis, this number is expected to rise dramatically.
Prevention
There is
no
specific treatment to
prevent erectile dysfunction. Perhaps the most important measure is
to
maintain generalgood health and avoid atherosclerosis by
exercising regularly, controlling weight, controlling hypertension and highcholesterol levels, and not smoking. Avoiding excessive alcohol intake may also help.
Resources
Books
Icon Health Publications. The Official Patient's Sourcebook on Erectile Dysfunction: A Revised and Updated Directory forthe Internet Age. San Diego: Icon Health Publications, 2005.
Kloner, Robert A. Heart Disease and Erectile Dysfunction. Totowa, NJ: Humana Press, 2004.
Lue, Tom F. An Atlas of Erectile Dysfunction, Second Edition. London: Taylor & Francis Group, 2003.
Metz, Michael E. and Barry W. McCarthy. Coping With Erectile Dysfunction: How to Regain Confidence and Enjoy GreatSex Oakland, CA: New Harbinger Publications, 2004.
Periodicals
Roberts, Shauna S. "Options Increase for Men With Erectile Dysfunction: Doctors Now Have an Array of Treatments forMen's Sexual Problems." Diabetes Forecast (September 2004): 55-58.
Sadovsky, Richard. "Sildenafil is Safe and Effective in Men With Stable CAD." American Family Physician (September 1,2004): 955.
Tomlinson, John. "The Patient With Erectile Dysfunction." The Practitioner (February 9, 2005): 104.
Trissel, Lawrence A. "Long-Term Stability of Trimix: A Three-Drug Injection Used to Treat Erectile Dysfunction." InternationalJournal of Pharmaceutical Compounding (May-June 2004): 231-235.
Wooten, James M. "Erectile Dysfunction: There are Now Three Effective Oral Drugs for Treating ED, Paving the Way forNurses to Put Patients With This Condition on the Road to Good Sexual Health." RN (October 2004): 40.
Zoler, Mitchel L. "Drug Update: Erectile Dysfunction." OB/GYN News (April 15, 2004): 92.
Organizations
Erectile Dysfunction Information Center. 10949 Bren Road East, Minnetonka, MN
55343-9613. (866) 294-7508.publisher@erectile-dysfunction-impotence.org. http://www.cure-ed.org.
952-852-5560
Other
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
