Oral Sildenafil in the Treatment of Erectile Dysfunction

Irwin Goldstein, Tom F. Lue, Harin Padma-Nathan, Raymond C. Rosen, William D. Steers, Pierre A. Wicker, for the Sildenafil Study Group
N Engl J Med 1998;338:1397-404

BACKGROUND -- Sildenafil is a potent inhibitor of cyclic guanosine monophosphate in the corpus cavernosum and therefore increases the penile response to sexual stimulation. We evaluated the efficacy and safety of sildenafil, administered as needed in two sequential double-blind studies of men with erectile dysfunction of organic, psychogenic, or mixed causes.

METHODS -- In a 24-week dose-response study, 532 men were treated with oral sildenafil (25, 50, or 100 mg) or placebo. In a 12-week, flexible dose-escalation study, 329 different men were treated with sildenafil or placebo, with dose escalation to 100 mg based on efficacy and tolerance. After this dose-escalation study, 225 of the 329 men entered a 32-week, open-label extension study. We assessed efficacy according to the International Index of Erectile Function, a patient log, and a global-efficacy question.

RESULTS -- In the dose-response study, increasing doses of sildenafil were associated with improved erectile function (P values for increases in scores for questions about achieving and maintaining erections were <0.001). For the men receiving 100 mg of sildenafil, the mean score for the question about achieving erections was 100 percent higher after treatment than at base line (4.0 vs. 2.0 of a possible score of 5). In the last four weeks of treatment in the dose-escalation study, 69 percent of all attempts at sexual intercourse were successful for the men receiving sildenafil, as compared with 22 percent for those receiving placebo (P<0.001). The mean numbers of successful attempts per month were 5.9 for the men receiving sildenafil and 1.5 for those receiving placebo (P<0.001). Headache, flushing, and dyspepsia were the most common adverse effects in the dose-escalation study, occurring in 6 percent to 18 percent of the men. Ninety-two percent of the men completed the 32-week extension study.

CONCLUSIONS -- Oral sildenafil is an effective, well-tolerated treatment for men with erectile dysfunction.

Source Information
From the Department of Urology, Boston University Medical Center, Boston (I.G.); the Department of Urology, University of California, San Francisco (T.F.L.); the Department of Urology, University of Southern California, Los Angeles, and the Male Clinic, Santa Monica, Calif. (H.P.-N.); the Department of Psychiatry, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, N.J. (R.C.R.); the Department of Urology, University of Virginia, Charlottesville (W.D.S.); and Pfizer Central Research, Groton, Conn. (P.A.W.). Address reprint requests to Dr. Goldstein at the Department of Urology, Boston University Medical Center, 720 Harrison Ave., P (606), Boston, MA 02118.

The members of the Sildenafil Study Group are listed in the Appendix.

The other members of the Sildenafil Study Group are S. Auerbach, Newport Beach, Calif.; A.L. Burnett, Baltimore; R. Castellanos, Fort Myers, Fla.; L. Charles, Stratford, N.J.; F. Eid, New York; R. Feldman, Waterbury, Conn.; W. Fitch III, San Antonio, Tex.; T. Garland, Lawrence, N.J.; M. Gittelman, North Miami, Fla.; D. Gleason, Tucson, Ariz.; F. Govier, Seattle; L. Hoffman, Gurnee, Ill.; J.M. Kaufman, Aurora, Colo.; I. Klimberg, Ocala, Fla.; V. Longo, New London, Conn.; T. Malloy, Philadelphia; A. McCullough, New York; J. McMurray, Huntsville, Ala.; D.F. Mobley, Houston; S. Morganstern, Atlanta; M. O'Leary, Boston; D. Ohl, Ann Arbor, Mich.; J. Rajfer, Torrance, Calif.; M.S. Rendell, Omaha, Nebr.; R. Shabsigh, New York; C. Steidle, Fort Wayne, Ind.; J Susset, Providence, R.I.; J. Tuttle, Lexington, Ky.; G. Wells, Birmingham, Ala.; C. White, Mobile, Ala.; J. Young, Laguna Hills, Calif.; and N. Zinner, Torrance, Calif.

Editorial Comment

Abstracts of these articles are available free of charge at PubMed.

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