Nov. 20 (Bloomberg) -- A spray-on treatment for premature ejaculation may help sufferers prolong sexual intercourse by as much as five times, doctors found.

The drug, which works by numbing the penis before sex, delayed orgasm by an average of 108 seconds, according to a study presented at a medical meeting in San Diego yesterday. The trial, involving 256 men in the U.S., Canada and Poland, found the treatment improved the sexual satisfaction of both patients and partners while causing no serious side effects.

The product incorporates two local anesthetics in an aerosol applied to the tip of the penis, according to Shionogi & Co., its Osaka, Japan-based developer. It aims to treat a sexual dysfunction affecting as many as a third of American men aged 18 to 59 years, Shionogi’s Sciele Pharma Inc. unit said in a statement. Johnson & Johnson said in February it won approval in Sweden and Finland for the first prescription pill to treat the problem, three years after U.S. regulators rejected the drug.

“Premature ejaculation can have a powerful negative impact on the emotional and sexual lives of men and their partners,” Stanley E. Althof, executive director of the Center for Marital and Sexual Health of South Florida, said in the statement. Shionogi’s results “seem to be a step in the right direction.”

Premature ejaculation is defined by the International Society for Sexual Medicine as the inability to delay ejaculation for more than 1 minute after vaginal penetration.

Patients taking Shionogi’s compound, called PSD502, took an average of 2.6 minutes to reach ejaculation, compared with 0.8 minute for those given a placebo, according to the results of the study presented yesterday at the annual meeting of the Sexual Medicine Society of North America Inc.

Sciele said in May it would prepare to submit the treatment for regulatory review in the first half of 2010.

Shionogi shares advanced 0.6 percent to 1,838 yen on the Tokyo Stock Exchange today, while Japan’s Topix Pharmaceutical Index, which tracks 33 of the country’s drugmakers, declined 0.6 percent.

To contact the reporter on this story: Kanoko Matsuyama in Tokyo at at kmatsuyama2@bloomberg.net.

Last Updated: November 20, 2009 02:35 EST