USRF Research

Impotency Update: Sildenafil (Viagra)

Leonard S. Marks, M.D.

Director, USRF

Spring, 1998 - Sildenafil (Viagra), the new oral agent for impotency from Pfizer, is being tested at USRF and other sites in the U.S. Study Group. At the 1997 meeting of the American Urological Association, the first results were presented. In this placebo-controlled study of 377 men, those treated with the new drug had significant improvement in achieving and maintaining erections and satisfaction with sexual intercourse. A benefit rate of 75%-80% was found in the 100 mg group, more than double that of the placebo group. These results are especially impressive since 90% of the men studied had an organic (physical) component to their erectile dysfunction. The drug was well-tolerated; side-effects were minor.

The drug was taken "as needed," i.e., one hour before anticipated sexual activity. Mechanism of action appears to be inhibition of Type V phosphodiesterase, which is localized to smooth muscle in the corpora cavernosa, resulting in increased blood flow.

USRF was one of the select clinical trial sites, and men in project are continuing in a long-term open-label study. The drug was approved by the U.S. FDA on March 27, 1998, after being "fast track" reviewed. The drug is expected to be in pharmacies nationwide by the end of April.

Breaking News: Viagra

Peer-Reviewed Articles of Interest:

1. Boolell, M. et al. Sildenafil: an orally active type 5 cyclic GMP-specific phosphodiesterase inhibitor for the treatment of penile erectile dysfunction. Int. J. Impot. Res. 8: 47-52, 1996.

2. Boolell, M. et al. Sildenafil, a novel effective oral therapy for male erectile dysfunction. Brit. J. Urol. 78: 257-261, 1996.


The NIH Consensus Statement on Impotency

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