Impotence is defined as a male's inability to achieve and maintain an erection necessary for sexual performance. The condition afflicts approximately 10-20 million men in the United States; however only 5-10% of patients receive treatment. Patients often report increasing anxiety, loss of self esteem, lack of self-confidence, tension, and difficulty with relationships.

What is the physiology of an erection?

Erection of the penis is attained by an increase in blood flow to the penis and diminished outflow. At full erection, flow of blood in and out of the penis is markedly reduced. In addition, nitrous oxide (NO) is released from nerve endings in the endothelial cells during sexual stimulation. An enzyme called guanylate cyclase is activated by NO. The enzyme's purpose is to increase levels of cGMP (Cyclic Guanosine Monophosphate). cGMP results in smooth muscle relaxation and allows for blood to flow into the penis. There are phosphodiesterases (PDE) which are responsible for degrading cGMP resulting in a loss of an erection.

In summary, erection of the penis is caused by

• Relaxation of smooth muscle
• Net inflow of blood into the penis
• Diminished outflow of blood

What are the causes of erectile dysfunction?

Erectile dysfunction can be divided into physical and psychological factors:

• Medications such as Beta-blockers (high blood pressure medications), sedatives, antidepressants, and alcohol can cause erectile dysfunction.
• Nerve impulse problems in men with diabetic vasculopathy, strokes, or spinal cord injuries.
• Surgery in patients who have had their prostate or bladder removed for cancer may experience erectile dysfunction. This is caused by an interruption/damage to the pelvic nerves and pudendal arteries which are common side effects of radical surgeries and not complications.
• Low levels of testosterone caused by chronic disease (commonly liver or heart problems) or simply by the aging process can be responsible for impotence.

Psychogenic stressors such as depression and martial discord are common causes of impotence.

Performance anxiety and fear of failure can prevent the erectile process which can lead to a vicious cycle.

What are the current treatments for impotence?

1. Vacuum constriction devices or rubber bands: These devices often interrupt the spontaneity of love making.

2. Penile injection: This is a very effective and proven method, but compliance is a problem . A substance called papaverine used to be injected, but now a prostaglandin (smooth muscle relaxant) can be injected. The duration of the erection will be dependent on the amount of medication injected.

3. Intraurethral suppository called MUSE (alprostadil) can be inserted into the urethra (where the urine comes out in the penis) 5 to 10 minutes prior to intercourse. This medication was launched by Vivus about one year ago.

What is VIAGRA (Sildenafil)?

Viagra is currently the only oral therapy for erectile dysfunction recently approved by the FDA on March 27, 1998. Made by pharmaceutical giant Pfizer, this little pill's popularity is far ahead of that of Fen-phen evidenced by 34,000 prescriptions written in the first week of its release vs. 5,000 prescriptions of Fen-phen in the first month.

How does Viagra work?

Please refer to first question of what causes an erection. Viagra (Sildenafil) prevents the phosphodiesterase namely type 5 (PDE5) from degrading cGMP (agent that causes smooth muscle relaxation essential for erection). Therefore, there is more cGMP around in the penile shaft to help with erection. Viagra should be taken about 30 minutes to an hour before the desired effect.

Tablets come in 25 mg, 50 mg, and 100 mg tablets. Without sexual stimulation Viagra will not cause an erection.

Who is a candidate for Viagra?

Viagra was not created to be an aphrodisiac. Viagra is indicated for treatment of erectile dysfunction which should be diagnosed by a clinician after a history and physical exam.

Impotence may be a sign of an underlying disease such as diabetes or hypertension.

Who should not use Viagra?

Viagra is contraindicated in men concurrently using organic nitrites. Caution should be used in patients with anatomical deformation of the penis (e.g. Peyronie's disease). Patients who have conditions such as sickle cell anemia, multiple myeloma, or leukemia may be an increased risk for priapism (prolonged erection which may cause penile necrosis) and should use Viagra with caution.

What are the side effects?

Headache and flushing were the two most common side affects. Mild impairment of blue/green color discrimination was seen at peak Sildenafil blood levels.

What is the cost?

About $10 a pill. Insurance companies may not cover the cost or may restrict the supply you get.

By doing the math, Viagra has to the potential to be $1 billion dollar a year business by virtue of its first week's sales. The potential of this drug to appeal to the masses has caught wall street's attention.

How effective is this drug?

A complied series of twenty-one studies done on 3000 patients over 5 years with various etiologies for erectile dysfunction resulted in statistically significant improvement compared to placebo.

Patients taking Viagra had a 66% rate of successful intercourse (ability to achieve and maintain an erection satisfactory for intercourse) vs. 20% on placebo. 88% of patients reported that Viagra improved their erections.

Are there more drugs in the pipeline?

Zonagen's Vasomax (produced under license of Schering-Plough) has a mechanism similar to Viagra and could come out as early as late 1998.

A topical gel is undergoing trials.

A competitive vitamin supplement Vaegra was available over the Internet. Pfizer sued the two outfits for trademark infringement.

A word of caution:

There are numerous Web sites on the Internet advertising Viagra. One site run by a urologist offered a phone consultation and a Viagra prescription for $50. Other sites will mail or fax you a prescription for a certain fee. Viagra should be prescribed to a patient only after he is evaluated and examined by a physician. A physician who never sees his patients is in no position to look for potential side effects.

There is certainly a potential for marketing abuse and mislabeling of this drug as a sexual enhancement medication. Black markets exist in other countries where Viagra is sold at 5-10X the original cost. Long term side effects have not been clearly established; a classic example is Phen-fen which caused valvular disease of the heart. Any one buying this drug without a prescription or without seeing a doctor should heed-caveat emptor!

If you or someone you know has a problem with impotence, consult your primary care doctor or urologist to discuss your problem and treatment options.

Ryan K. Lee is a physician specializing in Obstetrics and Gynecology. He is currently in private practice in Glendale and Los Angeles, California.