Nov. 19, 2009 — An investigational drug that didn’t perform well as anantidepressant appears to slightly boost sexual desire as well as thenumber of satisfying sexual encounters in women with lagging libidos, a studyshows.
The research was presented this week at the 12th Congress of the EuropeanSociety for Sexual Medicine in Lyon, France.
Some wonder if the drug, called flibanserin, will be the new ”femaleViagra,” but critics say the effect is minimal. Meanwhile, the manufacturer isplanning additional clinical trials and expanding the participant pool toinclude older women.
The big news, according to those who studied flibanserin? “There issomething that works on the neurotransmitters in the central nervous system toalter sexual desire in a positive way,” says John M. Thorp Jr., MD, McAllisterdistinguished professor of obstetrics and gynecology at the University of NorthCarolina at Chapel Hill School of Medicine, and a principal investigator forthe U.S. trials.
At the Congress, researchers reported the pooled results for 1,378premenopausal women, average age 35, who took 100 milligrams of the drug or aplacebo pill during a 24-week period. The trials were in Europe and NorthAmerica. The women kept track of the number of satisfying sexual encounters –defined as intercourse, oral sex, masturbation, or genital caressing by theirpartners. All women had to be in a stable, monogamous relationship. All womenhad a diagnosis of hypoactive sexual desire disorder (HSDD), marked by adecrease or absence of sexual desire accompanied by distress in thepatient.
When researchers compared sexual desire and events during the last fourweeks to the first four weeks, they found that those on the medication wentfrom 2.8 sexually satisfying events in the first four weeks to 4.5 in the finalfour weeks. Those on placebo went from 2.7 to 3.7.
”The difference was [about] one additional satisfying sexual encounter amonth,” says Thorp.
The study also shows the drug improved sexual functioning and distressrelated to the sexual problems.
About 15% of the women taking the medication dropped out due to adverseevents, according to information from Boehringer Ingelheim Pharmaceuticals,which makes the medications, while 7% of women on placebo discontinued thestudy. Among the most commonly reported side effects were daytime sleepiness,dizziness, anxiety, and fatigue.
How Flibanserin Works
Exactly how flibanserin improves sexual desire isn’t known for sure. “Wethink it modulates neurotransmitters involved in sexual functioning,” saysMichael Sand, PhD, MPH, director of clinical research and team leader,flibanserin, for Boehringer Ingelheim.
”It interacts with [neurotransmitters] serotonin and dopamine in thecentral nervous system,” Thorp says.
Originally studied as an antidepressant by Boehringer Ingelheim, the drugdidn’t prove effective for depression. But when researchers noticed reports ofimproved sexual desire in some participants, the research changed focus.
As for critics, Thorp acknowledges that ”there are multiple criticisms [ofthe studies] that are justifiable. One is the whole measurement issue and howdo you quantify an objective response? That’s particularly hard when thedisorder is subjective.”
He notes, too, that the placebo group also saw improvement. “There was a bigplacebo effect,” he says, noting that attention from a concerned doctor mayalso contribute to improvement in the sexual functioning of women withHSDD.
“The data look good,” says Kathleen Segraves, PhD, associate professor ofpsychiatry at Case Western Reserve University in Cleveland and a sextherapist who reviewed the data for WebMD. “But only clinical experience andactual practice will reveal how clinically useful the effect is.”
Case Western Reserve was one of the U.S. study sites for flibanserin, butSegraves was not involved in the study.
The real world, she says, is different from clinical trials. For instance,in the study, each woman kept an e-diary to assess her level of desire daily.That exercise may have kept women focused on the problem, Segraves says, andperhaps more motivated.
To call flibanserin the female Viagra, however, is incorrect, she says.”Viagra is a vasodilator. It only makes the penis hard, it doesn’t work on thedesire of a man. It may give him more confidence. It gives him a reliableerection. It inflates the penis. He still needs to have desire.”
The differences in the number of satisfying sexual encounters may seemsmall, Segraves says. But it would probably not be considered small by thewomen who have the condition, she says.
“You have to remember these women have lost desire over time and for sometime. You have to remember these women [with no sexual desire] are verydistressed by it. If you go from zero to one, you’re pleased as punch, becauseyou were flat-lining before.”
Some wonder if developing a pharmaceutical for women’s lagging desire ismore about business than pleasure. “We need to address multiple factors thatunderlie sexual desire,” says Gina Ogden, PhD, a sex therapist in Cambridge,Mass., and author of The Return of Desire. Of the development offlibanserin, she says: “I think the focus is more to line the pockets of thepharmaceutical companies than to address the real and multiple factors involvedin women’s sexual desire.” A woman’s desire, says Ogden, is influenced by manyfactors, including her feelings about sex, what sex means to her, and whattypes of intimacy she prefers.
Boehringer Ingelheim is continuing studies. Recruitment of bothpremenopausal and postmenopausal women with HSDD for new clinical trials isbeginning, Sand says.
He wouldn’t comment on a possible timeline of when the drugmaker might askfor FDA approval or when it may be on the market.