Men who suffer from premature ejaculation might be able to boost their endurance by as much as six times with an experimental spray solution that gently numbs the penis, according to a study recently published in the British Journal of Urology.

The numbing spray, PSD502 (made by a London company called Plethora Solutions), contains two local anesthetics: lidocaine and prilocaine, drugs that dampen sensation. The study included 300 heterosexual men in the U.K., Czech Republic, Hungary, and Poland suffering from premature ejaculation, which is characterized by "ejaculation which always or nearly always occurs prior to or within about one minute of vaginal penetration," according to the International Society for Sexual Medicine. The study found that applying the spray five minutes before sex increased the men's stamina from an average 36 seconds to nearly four minutes.

The spray has not been approved for sale in the U.S. or any other country, according to study co-author Wilbert Wallace Dinsmore, a sexual medicine physician at the Royal Victoria Hospital in Belfast, Ireland. Dinsmore works as an investigator and consultant for Plethora Solutions, but he tells ScientificAmerican.com that he is not on the company's payroll. The other author of the study, Michael Wyllie, is the co-founder and chief technical officer of Plethora and serves as an assistant editor of the British Journal of Urology (where the study is published), according to the company Web site.

Thomas Walsh, a urologist at the University of Washington School of Medicine in Seattle, says that using local aesthetics to treat premature ejaculation is nothing new; urologists have been giving patients off-label prescriptions for anesthetic gels and creams for decades. (The most common treatment for the condition is counseling with a sexual therapist, but it's not uncommon for some patients to use the anesthetics too, he adds.)  Walsh says, however, that the skin appears to soak up PSD502 rapidly unlike creams and gels that are slowly absorbed, which means they can rub off on a woman and decrease her sensation, too.

Research suggests that premature ejaculation affects 30 to 40 percent of men at some point in their lives, but Walsh suspects this is just the tip of the iceberg. "Men have a lot of inhibitions sharing these issues with their providers," he says. There are currently no drugs approved by the U.S. Food and Drug Administration to treat the condition, according to Walsh.

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