Viagra: How Well Does it Work?

Now that Viagra has been on the market for about a year, the impotence drug appears to have a lower rate of efficacy than originally reported. At the annual meeting of the American Urological Association (Oncology Times, 9/99), Jacob Rajfer, MD, explained that the 80% success rate widely reported when Viagra was approved by the FDA came from studies that included men with all forms of erectile dysfunction.

As the research continues, doctors are finding that the efficacy rate differs according to the reason for erectile dysfunction. For example, Dr. Rajfer, who is a professor of urology at the Harbor-UCLA Medical Center in Los Angeles, said that the highest failure rate occurred in men who had a form of radical prostatectomy that damaged some of the nerves crucial to an erection. On the other hand, the highest success rate (90%) occurs in men with spinal cord injuries and psychogenic erectile dysfunction. When men with one or the other of the latter two causes of impotence were excluded from Dr. Rajfer's UCLA study, Viagra's success rate dropped to 64%.

The nerve-sparing radical prostatectomy was introduced about 20 years ago to preserve sexual function, though it fails to do so in about 35-60% of cases. Only 25% of men whose erectile dysfunction occurred after this type of prostatectomy had a good response to Viagra, according to a team of researchers from Nashville who presented their work at the urology meeting. Dr. Rajfer noted that 130 American men died while taking Viagra as of March 1999, most of cardiovascular events. Headaches are the most commonly reported side effect, with gastrointestinal upset as a close second.

Urologists were warned that the major caveat surrounding Viagra was its potential for causing catastrophic hypotensive events in patients with cardiovascular disease who are taking nitrates. An Italian research team found that men with chronic stable angina can take Viagra if their symptoms and exercise tests showed that their condition has been controlled with beta-blocker drugs.

Doctors at the urology meeting were reminded that Viagra is not an aphrodisiac and does not have an effect on libido. "A man must be aroused sexually for the drug to have an effect."

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