New drug treats premature ejaculation

SAN ANTONIO, May 24 (UPI) -- Dapoxetine, a new drug meant to treat premature ejaculation in men, could make a bigger impact on the male sexual health market than Pfizer's impotence blockbuster Viagra.

"Premature ejaculation is the most common male sexual dysfunction," said Dr. Jon Pryor, professor and chairman of the department of urologic surgery at the University of Minnesota's Twin Cities Campus in Minneapolis. "About 20 percent of adult males have premature ejaculation at any one time, and 70 percent of men experience premature ejaculation at some time during their lives."

At the annual meeting of the American Urological Association in San Antonio, Pryor described clinical trials involving 2,614 men and their heterosexual partners who were willing to time their sexual activities with stopwatches in order to conduct the trial with the experimental drug. Dapoxetine is being developed by Ortho Urology, a division of Johnson & Johnson in New Brunswick, N.J.

Pryor said Ortho Urology had filed an application with the Food and Drug Administration for approval of dapoxetine for premature ejaculation. He added approval might occur within a year.

As soon as it receives FDA approval, the potential market for dapoxetine is huge, though doctors said how successful it will be in the marketplace depends on a number of factors.

"A lot will depend on how aggressively the company that makes dapoxetine will use direct-to-consumer advertising for premature ejaculation," said Dr. Jonathan Jarow, professor of urology at The Johns Hopkins University in Baltimore.

He noted that aggressive advertising for the erectile dysfunction drugs Viagra, Levitra and Cialis have created a major market -- yet the vast majority of the 30 million Americans with erectile dysfunction have not sought treatment. He said the same problems that make men reluctant to discuss and treat erectile dysfunction could impact sales of treatments for premature ejaculation.

Jarow said other drugs in the same class as dapoxetine are now prescribed by doctors for premature ejaculation and are recognized by the American Urological Association as treatments for the condition, but prescriptions of these medications -- called selective serotonin re-uptake inhibitors -- are for off-label use and therefore their manufacturers cannot advertise them for that purpose.

Pryor said study participants who took dapoxetine were able to increase their time to ejaculation significantly --from less than one minute to more than three minutes following vaginal penetration. He said normal time to ejaculation during sexual intercourse is about 7 to 9 minutes.

In addition to prolonging time to ejaculation, Pryor said, "Sexual satisfaction was improved by both the men and the partners who each filled out questionnaires regarding the experience with dapoxetine." He noted studies on sexual satisfaction often are performed only on one member of the partnership.

"The results with dapoxetine are compelling," Pryor said. "They demonstrate that, for the first time, a medicine can be taken by men on an on-demand basis and provide significant improvement in their premature ejaculation condition." He also said side effects from the drug were mild and infrequent.

Pryor reported on two identical studies in which premature ejaculating men were assigned either a placebo, a 30-milligram dose of dapoxetine or a 60-milligram dose of dapoxetine. The men took the pills about an hour before sexual activity and their partners were provided with stopwatches. The partners started the watches at the moment of vaginal penetration and stopped the timers upon ejaculation.

Before the trial, the study participants averaged 0.91 minutes before ejaculating during sexual intercourse. After 12 weeks of treatment, the 783 men on placebo averaged about 1.94 minutes before ejaculating, the 798 men on the 30-mg dose of dapoxetine ejaculated after an average of 3.02 minutes, and the 758 men on the 60-mg dose ejaculated after an average of 3.65 minutes. Researchers reviewed the patients' time scores every three weeks.

Pryor said perhaps even more important than the prolonged time to ejaculation were the scores of patients on tests of control of ejaculation and other factors related to satisfaction. Before the trial, he said, only 2 percent to 3 percent of the men said they felt control over ejaculation. After the trial about 25 percent of men on placebo said they controlled ejaculation, 50 percent of those on 30 mg of dapoxetine said they controlled ejaculation, 58 percent of those on 60 mg of dapoxetine said they controlled ejaculation.

At the start of the trial, about 21 percent of men on placebo said they were satisfied with their sexual relationship, after the trial 25 percent of those men said they were satisfied. About 21 percent of men taking the 60 mg dose of dapoxetine expressed satisfaction with their sexual lives before the trial started compared with 57 percent at the end of the trial.

At the start of the trial about 20 percent of the partners of the men on placebo were satisfied with their sexual relationship, and after the trial 25 percent of those women said they were satisfied. About 24 percent of the partners of men taking the 60 mg dose of dapoxetine expressed satisfaction with their sexual lives before the trial started compared with 58 percent of those women at the end of the trial.

When one considers that many couples would not participate in the trial when stopwatches ware mentioned, the couples in the trial had to have been highly motivated, suggested Dr. Gregory Broderick, professor of urology at the Mayo College of Medicine, Rochester, Minn.

"I think that means the participants in the study may have had the worse cases of premature ejaculation," Broderick said Monday. He moderated a press briefing that included the details on dapoxetine. "I would expect the numbers to be better if the drug is approved and is used by people without severe premature ejaculation."

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Ed Susman covers medical research for UPI Science News. E-mail: sciencemail@upi.com