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New drug stimulates sexual desire in women in clinical trial

November 16, 2009 |  2:59 pm

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An experimental non-hormonal drug helped women increase their sexual desire and satisfaction and reduced the distress associated with lack of desire, researchers reported today. The clinical trial in 1,378 premenopausal women will provide the drug's manufacturer, Boehringer-Ingelheim Pharmaceuticals of Germany, ammunition to approach the Food and Drug Administration for approval of the drug, but it is not clear what that agency will do. An earlier hormonal drug that produced a similar success rate was rejected by the agency largely because its advisers feared widespread abuse.

The need for artificial enhancement of sexual desire is perceived to be just as strong for women as the desire to correct erectile dysfunction in men. A recent survey (sponsored by Pfizer) of 31,000 women found that as many as 43% had some form of sexual dysfunction. About one in 10 suffered from sufficient lack of desire for it to be distressing for them.

The most common treatments for female sexual dysfunction now are creams spread on the vagina that lead to engorgement of blood vessels in the hope that this will stimulate desire. These don't work well. Procter & Gamble developed a slow-release testosterone patch that trials showed produced about 1.5 extra satisfying sexual episodes per month beyond those produced by a placebo. The patch has been approved in several countries in Europe, but in 2004, the FDA rejected it, citing fears of widespread off-label use and a potential for increased risk of strokes in women who were also taking estrogen.

The new drug is the first to work on the brain rather than attempting to physically stimulate a woman's body. Called flibanserin, it stimulates one serotonin receptor in the brain and blocks a second one. The overall effect is a lowering of serotonin levels and a reduction in inhibitions. The drug was originally developed in the 1990s as an anti-depressant, but by 2002, the company had discovered that it didn't work very well for that purpose. But one side effect observed in both humans and animals was a stimulation of libido in women, and the new trials were designed to test that.

The trials involved more than 5,000 European and American women who received either doses of flibanserin ranging from 25 to 100 milligram per day or a placebo. The drug had no effect in women who received less than 100 milligram per day, however, so only those receiving the highest dose were included in the results reported today at the 12th Congress of the European Society for Sexual Medicine in Lyon, France.

In a telephone news conference, Dr. Anita Clayton of the University of Virginia, who led the study, said that women receiving that dosage had an average of 1.7 satisfying sexual events each month beyond the baseline level of 2.7 events. Those receiving the placebo had an 0.8-event increase. The women also scored significantly higher on measures of sexual desire and significantly lower on scales of distress related to their sexual functioning, she said.

At the beginning of the study, she added, the women were having sex about five times a month, with most episodes initiated by their partner and only half of them satisfying. The observed increase "should be considered quite meaningful," Clayton said. The first increase in desire, she said, came about four weeks after the beginning of treatment. The most common side effects were dizziness, nausea, fatigue and daytime sleepiness; most of those disappeared after the women had been on the drug for a while. About 15% of women receiving the drug dropped out of the study because of side effects, compared to 7% of those receiving the placebo.

The drug "may, over time, prove to be an effective treatment without the side effects of androgen replacement therapy, which is  the only treatment currently available," said Dr. John M. Thorp Jr. of the University of North Carolina School of Medicine, who presented the report in France.

Not everyone thinks the drug is a good idea, however. Liz Canner, director of the new documentary "Orgasm Inc." about the efforts to develop such drugs, said the flibanserin "doesn't deal with what causes low libido: relationship problems, stress and so forth. The idea that we can go in and change the brain by lowering inhibitions is quite disturbing."

The studies were funded by Boehringer-Ingelheim.

-- Thomas H. Maugh II

Photo: Ladies, if this doesn't whet your desire, there may be a new drug for you. Pictured, James Ellis. Credit: David Myrick

 

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