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A German pharmaceutical company is touting one of its failed antidepressants as a libido-boosting drug for women.

Flibanserin can increase sexual desire in women suffering from "hypoactive sexual desire disorder," according to three clinical trials funded by the company, Boehringer Ingelheim. The results were presented yesterday at the Congress of the European Society for Sexual Medicine in Lyon, France.

The disorder is a branch of "female sexual dysfunction," a widely debated term that involves everything from an inability to reach orgasm to a lack of desire.

Described as a "Viagra-like drug for women" by one of the trials' principal investigators, flibanserin is prompting an outcry from critics who say female sexual dysfunction is a disorder the pharmaceutical industry has conjured as an attempt to capitalize on women's complex sexuality.

In two North American trials, the company surveyed 1,378 women with hypoactive sexual desire disorder. Another trial was conducted in Europe.

According to the Diagnostic and Statistical Manual of Mental Disorders, a reference guide for the medical profession, the condition is accompanied by a persistent absence of sexual fantasies or desire for any form of sexual activity. The disorder is marked by distress and difficulties in a relationship.

The North American study participants, aged 18 or older but premenopausal, were all in "stable, communicative, monogamous, heterosexual relationships" for at least one year. The women were asked to report the number of sexual events they experienced every month, from sexual intercourse and oral sex to masturbation or genital stimulation by their partner and were also asked whether the event was satisfying for them. They were surveyed over half a year.

The researchers found that women who had fewer than three sexually satisfying experiences a month at the start of the trials were having 4.5 when they took 100 milligrams of flibanserin daily - compared with 3.7 who took a placebo. They say the drug also improved the women's sexual desire, as measured by the entries they kept in an electronic diary.

Flibanserin acts on serotonin, a chemical messenger in the brain thought to play a role in sexual response, Elaine Jolly, professor of obstetrics and gynecology at the University of Ottawa and one of the Canadian physicians participating in the trials, said in a statement issued by the company yesterday.

John Thorp, a principal investigator for the North American trials, said the pink Viagra moniker is apt. Even as hypoactive sexual desire disorder continues to baffle experts, Dr. Thorp argued, it is as much of a problem for women as erectile dysfunction is for men.

"I don't know if it's a psychological or biological thing, but once they get interested things work fine," said Dr. Thorp, professor of obstetrics and gynecology at the University of North Carolina at Chapel Hill's school of medicine.

But critics take issue with those triumphantly terming this the female Viagra: While Viagra is used to treat erectile dysfunction by regulating blood flow in the penis, flibanserin is intended to treat a more nebulous, possibly psychological condition by manipulating serotonin.

They also question whether female sexual dysfunction exists.

"How is a young woman supposed to know how much sexual desire she's supposed to have?" said Liz Canner, a U.S. documentary filmmaker who followed the pharmaceutical hunt for a female Viagra over nine years in her film Orgasm Inc.

"In order to be diagnosed with this disease, the woman has to self-report that she's distressed by [her levels of sexual desire] which is very concerning because it's not like there's any normal here. It's not like you're supposed to have 20 sexual thoughts a day."

Ms. Canner was also concerned about the efficacy of the drug, which produced less than one more sexual event on average a month than a placebo.

"Women are going to be taking this daily and probably for years at a time and the long-term effects are unknown. For such little efficacy, it seems highly risky."

(The most major short-term effect was daytime sleepiness, but Dr. Thorp said that subsided after one week. Other adverse effects included dizziness, anxiety, dry mouth, nausea and insomnia.)

For the treatment of female sexual dysfunction, only Intrinsa, a testosterone patch made by Procter & Gamble, has been approved - and that is only in the European Union for women who have had radical hysterectomies and are taking estrogen. Several companies are also developing testosterone sprays.

Boehringer Ingelheim is now looking to test how women will react when they take the drug alongside antidepressants. Barring safety concerns, Dr. Thorp said, the company is hoping to obtain approval from the U.S. Food and Drug Administration within two years.

"Well, the companies definitely want to make money and this is a huge market," Dr. Thorp said.

"Is it disease or not? I don't know. Certainly nobody's going to die from it. … It is in the mode of trying to alter or improve lifestyle, or quality of life."

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