SAN FRANCISCO, CA, May 10, 2004 - Data from a study presented today show that daily treatment with Viagra® (sildenafil citrate) produced sustained improvements in erectile function among men who had undergone bilateral nerve-sparing retropubic radical prostatectomy (BNSRRP), a surgical procedure for prostate cancer. Findings from the study, which were presented at the 99th Annual Meeting of the American Urological Association, showed that patients using Viagra nightly for nine months experienced significant increases in normal erectile function and nocturnal erections compared to patients on placebo.

"Our study suggests that sustained, long-term rehabilitation of erectile function is possible," noted Laurence Levine, investigator and Professor, Department of Urology, Director, Male Sexual Function and Fertility Program, Rush University Medical Center. "These findings may signify a new era in enhancing the recovery of erectile function in this patient population."

Erectile dysfunction (ED) is seen in more than 90 percent of patients undergoing BNSRRP. Researchers believe that ED following surgery is initially related to trauma to the nerves that supply the penis and allow it to relax and fill with blood during an erection. Men normally have nocturnal erections during sleep, which aid the tissues of the penis in receiving adequate blood flow and oxygenation to remain healthy since these are minimal when the penis is flaccid. It is believed that, by disturbing this mechanism as a result of the prostate surgery, nocturnal erections do not occur and there is inadequate blood flow to the penis. If this persists, over time, the penile tissues will degenerate and be replaced with fibrous tissue. Even if nerve function is restored many months later, the tissue will be unable to respond when stimulated and a permanent condition of ED can result.

"The implications of this study are that physicians may have a dramatic, one-shot chance to prevent erectile dysfunction following a radical prostatectomy. We don't know the exact mechanism that is involved in this ED prevention - it may be neuronal regeneration, improvement in endothelial function or another mechanism other than PDE5 inhibition. Until there are further studies, Viagra remains the only drug with data for the prevention of ED in men undergoing surgery for prostate cancer," noted Harin Padma-Nathan, lead investigator and clinical professor of urology at the University of Southern California Keck School of Medicine.

Study Design

A 36-week longitudinal analysis was conducted of a subset of 54 men from a larger study of men with prior normal erectile function who had experienced erectile dysfunction resulting from BNSRRP. This subset of patients had been tested specifically for nocturnal penile tumescence (or swelling) and rigidity (NPTR) using a device called a Rigiscan®. NPTR measurements include duration of nocturnal erections and the percentage of rigidity. Normal NPTR is defined as maintaining 55 percent penile rigidity for at least 10 minutes.

Study participants were randomized to receive Viagra 50 mg, Viagra 100 mg or placebo nightly for 36 weeks. The 54-patient subset had NPTR testing two consecutive nights at 4, 12, 24, 36 and 48 weeks after surgery (i.e., the last reading being 8 weeks after drug was stopped and the patients were on no treatment for their ED).

Results

After nine months, spontaneous erectile function returned in 29 percent of the patient subset treated with either dose of Viagra® (sildenafil citrate), versus 5 percent of patients treated with placebo. The greatest increase in the average amount of time patients could sustain penile base rigidity over 55 percent (BR55) occurred at 16 weeks after surgery. The average length of time patients sustained penile tip rigidity over 55 percent (TR55) also improved at 16 weeks, but the greatest increase was seen after 48 weeks, when responders treated with Viagra 100 mg were able to sustain TR55 for an average of 56 minutes; those treated with placebo were not able to achieve TR55 at all.

About Viagra

Viagra® (sildenafil citrate) is a prescription medication indicated for the treatment of ED. Viagra is available only from health care providers and should always be used in accordance with its approved labeling. Viagra is contraindicated in patients who use nitrates in any form at any time.

Please see full prescribing information for Viagra (25 mg, 50 mg, 100 mg) tablets at www.viagra.com

Contact: Paul Ewing
212-733-0179
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Source: Pfizer Inc.

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