Sildenafil Citrate Health Article

Definition

Sildenafil citrate (Viagra) is a medication used to treat erectile dysfunction (ED), or impotence, in men.

Purpose

Viagra treats erectile dysfunction, the inability to achieve and/or maintain an erection of the penis that is adequate for sexual intercourse. Ten to fifteen million men in the United States suffer from ED, and by age 65, up to 25% of men have experienced impotence problems. Erectile dysfunction can be caused by a number of physical and psychological conditions, including diabetes, depression, prostate cancer, spinal cord injury, multiple sclerosis, artherosclerosis, and heart disease. Injuries to the penis that cause nerve, tissue, or vascular damage can trigger impotence. It is also a common side effect of some prescription medications, including antihistamines, antidepressants, antihypertensives, antipsychotics, beta blockers, diuretics, tranquilizers, appetite suppressants, cimetidine (Tagamet), and finasteride (Propecia).

Although not approved for use in women, clinical studies have shown that sildenafil citrate may be effective in relieving female sexual dysfunction for some women. In one study, both female and male study participants who suffered from sexual dysfunction related to their use of psychotropic medications such as benzodiazepines reported an increase in arousal and overall sexual satisfaction when they began taking Viagra. Several studies have also indicated the drug may be effective in improving libido and arousal in women taking selective serotonin uptake inhibitors (SSRIs).

Another investigational study conducted by researchers at Johns Hopkins University School of Medicine in Baltimore, and published in the August 2000 issue of the Journal of Clinical Investigation found that Viagra may have additional clinical promise for people with diabetes beyond treating ED. In animal studies, Viagra was effective in relaxing the pyloric muscle of stomach, improving digestion and relieving the symptoms of gastroparesis. Up to 75% of people with diabetes suffer from gastroparesis, which causes bloating, nausea, loss of appetite, and vomiting. Further human studies are needed to evaluate Viagra's effectiveness in treating this common diabetic complication.

Because of its capacity to enhance nitric oxide production, sildenafil has been investigated as a possible treatment for other disorders that are caused by impaired nitric oxide production. One such disorder is esophageal motility dysfunction (achalasia), in which the smooth muscles of the esophagus and the cardiac sphincter remain constricted, causing difficulty in swallowing, regurgitation of food, and chest pain when eating. A study published in 2000 in the journal Gastroenterology found that sildenafil temporarily improved the condition in some patients by relaxing the lower esophageal muscles.

Precautions

Viagra is not labeled or approved for use by women or children, or by men without erectile dysfunction. The medication may also be contraindicated (not recommended for use) in patients with certain medical conditions.

Because sexual activity can stress the heart, men who have heart problems should check with their physician to see if sexual activity is recommended. Viagra may trigger temporary hypotension (low blood pressure) and is known to increase cardiovascular nerve activity, so it is prescribed with caution in men with a history of heart attack, artherosclerosis, angina, arrhythmia, and chronic low blood pressure problems. However, a study published in the March 15, 2001, British Medical Journal found no evidence that the drug causes a higher incidence of heart attack. Further long-term studies are needed to determine the full implications of sildenafil citrate on heart disease.

Anyone experiencing cardiovascular symptoms such as dizziness, chest or arm pain, and nausea when participating in sexual activity after taking Viagra should stop the encounter. They should also not take Viagra again until they have discussed the episode with their healthcare provider.

It is recommended that men with kidney or liver impairments, and men over age 65, start at the lowest possible dosage of Viagra (25 mg). Clinical studies have shown that the drug builds up in the plasma of these patients to a concentration that is three to eight times higher than normal. Caution is also recommended in prescribing the drug to individuals with retinitis pigmentosa, a rare genetic eye disorder. Viagra should not be taken more than once per day by anyone.

Viagra has not been studied for use on patients with stomach ulcers and bleeding disorders, and its safety in these individuals is unknown. Men who have either of these conditions should let their physician know before taking Viagra. It should also be used with caution in men with misshapen or deformed penises, such as those with Peyronie's disease, cavernosal fibrosis, or with angulation of the penis.

Men who take medications containing nitrates (e.g., nitroglycerin, isosorbide mononitrate, isosorbide dinitrate) should never take Viagra, as the interaction between the two drugs may cause a dramatic drop in blood pressure, and possibly trigger a heart attack or stroke. This includes illegal recreational drugs such as amyl nitrates (also known as poppers).

Viagra may also interact with other prescription and over-the-counter (OTC) medications, either magnifying or diluting the intended therapeutic effects of one or both drugs. Some drugs that have a known interaction with Viagra include the protease inhibitor ritonavir and the antibiotic erythromycin. For this reason, it is critical that men who are prescribed Viagra let their healthcare providers know all the medications they are taking.

Other medications and therapies for erectile dysfunction, including vacuum or pump devices, drug injections (Caverject), and urethral suppositories (MUSE), should never be used in conjunction with Viagra.