About one in 10 women are thought to suffer from sufficient lack of sexual desire for it to be distressing for them. But few good therapeutic options exist. The most common treatments for female sexual dysfunction currently are creams spread on the vagina that lead to engorgement of blood vessels.
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 clinical trials involved more than 5,000 European and American women who received either a placebo or doses of flibanserin ranging from 25 milligrams to 100 milligrams per day. The drug had no effect in women who received less than 100 milligrams per day, researchers reported 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 women receiving the highest 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 a 0.8-event increase. The women also scored significantly higher on measures of sexual desire and significantly lower on scales measuring distress related to their sexual functioning, she said.
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 with 7% of those receiving the placebo.
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 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.