Impotence (ED) (cont.)
What medications are used to treat erectile dysfunction?
Medications for erectile dysfunction include:
How effective is testosterone in treating erectile dysfunction?
In patients with hypogonadism, testosterone treatment can improve libido and
erectile dysfunction, but the response of erectile dysfunction in men with
hypogonadism to testosterone is not complete; many men still may need additional
oral medications such as sildenafil, vardenafil or tadalafil.
In men 40 years of age or older, a breast examination, digital examination of
the prostate and a PSA level (prostate specific antigen) should be done to
exclude breast and prostate cancer before starting testosterone treatment since
testosterone can aggravate breast and prostate cancers. Patients who have breast
and prostate cancers or are suspected of having them should not use
testosterone.
Oral phosphodiesterase type 5 (PDE5) inhibitors
Sildenafil (Viagra)
What is sildenafil (Viagra)?
Sildenafil (Viagra) was the first oral phosphodiesterase type 5 (PDE5)
inhibitor approved by the FDA in the United States for the treatment of
erectile dysfunction (it is not approved for women). Sildenafil inhibits
PDE5, which is an enzyme that destroys cGMP. By inhibiting the destruction of cGMP by PDE5,
sildenafil allows cGMP to accumulate. The cGMP in turn prolongs relaxation of the smooth
muscle of the corpora cavernosa. Relaxation of the corpora cavernosa smooth muscle allows
blood to flow into the penis resulting in increased engorgement of the penis. In short,
sildenafil increases blood flow into the penis and decreases blood flow out of the penis.
How effective is sildenafil (Viagra)?
Sildenafil is used for the treatment of erectile dysfunction of either
physical or psychological cause. It has been found to be effective in treating
erectile dysfunction in men with coronary artery disease, diabetes mellitus,
hypertension, depression, coronary artery bypass surgery, and men who are taking
antidepressants and several classes of anti-hypertensives.
In randomized controlled trials, an estimated 60% of men with diabetes, and
80% of men without diabetes experienced improved erections with sildenafil.
How should sildenafil (Viagra) be administered?
Sildenafil is available as oral tablets at doses of 25, 50, and 100 mg. It
should be taken approximately one hour before sexual activity. In some men, the
onset of action of the drug may be as early as 11-20 minutes. Sildenafil should
be taken on an empty stomach for best results since absorption and effectiveness
of sildenafil can be diminished if it is taken shortly after a meal,
particularly a meal that is high in fat.
What is the dose of sildenafil (Viagra)?
In prescribing sildenafil, a doctor considers the age, general health status,
and other medication(s) the patient is taking. The usual starting dose for
most men is 50 mg, however, the doctor may increase or decrease the dose depending on
side effects and effectiveness. The maximum recommended dose is 100 mg every 24
hours, however, many men will need 100 mg of sildenafil for optimal effectiveness, and
some doctors are recommending 100 mg as the starting dose.
Metabolism (breakdown) of sildenafil is slowed by aging, liver and kidney
dysfunction, and concurrent use of certain medications (such as erythromycin--an
antibiotic, and protease inhibitors, for HIV). Slowed breakdown allows sildenafil
to accumulate in the body and potentially may increase the risk of side effects.
Therefore in men over 65, in men with substantial kidney and liver disease, and
in men who also are taking protease inhibitors, the doctor will initiate
sildenafil at a lower dose (25 mg) to avoid accumulation of sildenafil in the
body. A protease inhibitor ritonavir (Norvir) is especially potent in increasing
the accumulation of sildenafil, thus men who are taking Norvir should not take
sildenafil doses higher than 25 mg and at a frequency of no greater than once in
48 hours.
What are the side effects of sildenafil (Viagra)?
Sildenafil has been found to be well tolerated without important side
effects. The reported side effects are usually mild, and include headache,
flushing, nasal congestion, nausea, dyspepsia, diarrhea, and abnormal vision
(seeing a bluish hue or brightness).
Sildenafil can cause hypotension (abnormally low blood pressure that can lead
to fainting and even shock) when given to patients who are taking nitrates.
Therefore, patients taking nitrates daily, even patients taking nitrates only once a day, should not take sildenafil.
Nitrates are used most commonly to relieve angina (chest pain due to
insufficient blood supply to the heart muscle because of narrowing of the
coronary arteries); these include nitroglycerine tablets, patches, ointments,
sprays, and pastes, as well as isosorbide dinitrate, and isosorbide mononitrate.
Other nitrates such as amyl nitrate and butyl nitrate also are found in some
recreational drugs called "poppers".
Sildenafil should be used cautiously in men on alpha blockers such as
doxazosin (Cardura), terazosin (Hytrin), and tamsulosin (Flomax). There have been occasional reports of low
blood pressure in men who have taken the two classes of drugs simultaneously and
therefore it is recommended that there be at least a span of 4-6 hours between
the ingestion of sildenafil and alpha blockers.
There have been rare reports of priapism (prolonged and painful erections
lasting more than 6 hours) with the use of PDE5 inhibitors such as sildenafil, vardenafil, and tadalafil,
especially when sildenafil is used in combination with injection of medications
into the corpora cavernosa or intraurethral suppositories.
Patients with blood cell diseases such as
sickle cell anemia, leukemia, and multiple myeloma have higher than normal risks
of developing priapism.
Priapism untreated
can cause injury to the penis and lead to permanent impotence. Therefore,
sildenafil should not be used in combination with intraurethral suppositories
and corpora cavernosa injections. If there is prolonged erection (longer than 4
hours), immediate medical assistance should be obtained.
Is it safe for men with heart disease to use sildenafil (Viagra)?
Sildenafil has been found to be effective and safe in the treatment of
erectile dysfunction in men with stable heart disease due to atherosclerosis of
the coronary arteries, provided that they are not on nitrates. The real concern
is not as much the safety of sildenafil but the risk of sexual activity in
triggering heart attacks or abnormal heart rhythms in patients with heart
disease.
The risk of developing heart attacks or abnormal heart rhythms during sex is
low in men with well controlled hypertension, mild disease of the heart's
valves, well controlled heart failure, mild and stable angina (with a favorable
treadmill stress test), successful coronary stenting or bypass surgery, and a
remote history of heart attack (more than 8 weeks previously). Sildenafil can be
used safely in men in these low risk groups.
The risk of heart attack or abnormal heart rhythms during sex is higher in
men with unstable angina (angina that occurs at rest or with minimal exertion),
poorly controlled hypertension, moderate to severe heart failure, moderate to
severe disease of the heart's valves, recent heart attack (less than 2 weeks
previously), potentially life threatening disorders of heart rhythm such as
recurrent ventricular tachycardia, and moderate to severe disease of the heart's
muscle. In these men, doctors usually stabilize or treat the heart conditions
before prescribing sildenafil.
Before starting sildenafil for erectile dysfunction, a doctor may need to
determine whether the heart can safely achieve the workload necessary for sexual
activity. For example, in men with coronary artery heart disease, a doctor may
perform a treadmill stress test to determine whether there is adequate blood
supply to the heart muscle while exercising at levels comparable to sexual
activity.
Next: Intracavernosa injections »
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From the Doctors at MedicineNet.com  |
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- Penis Pump - Learn about penis pumps (vacuum constriction devices) for the treatment of erectile dysfunction (ED) or impotence. Pumps help a man maintain an erection. Source:WebMD Medical Reference from The Cleveland Clinic
- Testosterone Therapy to Treat ED - Erectile dysfunction (ED): testosterone replacement therapy for sexual health Source:WebMD Medical Reference from The Cleveland Clinic
- Diabetes - Information on Diabetes (Diabetes Mellitus) including types, causes, symptoms of diabetes, medications, and treatment. Produced by the doctors of MedicineNet.com Source:MedicineNet
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