WebMD Medical News
Louise Chang, MD
Nov. 19, 2009 -- An investigational drug that didn't perform well as an
antidepressant appears to slightly boost sexual desire as well as the
number of satisfying sexual encounters in women with lagging libidos, a study
The research was presented this week at the 12th Congress of the European
Society for Sexual Medicine in Lyon, France.
Some wonder if the drug, called flibanserin, will be the new ''female
Viagra," but critics say the effect is minimal. Meanwhile, the manufacturer is
planning additional clinical trials and expanding the participant pool to
include older women.
The big news, according to those who studied flibanserin? "There is
something that works on the neurotransmitters in the central nervous system to
alter sexual desire in a positive way," says John M. Thorp Jr., MD, McAllister
distinguished professor of obstetrics and gynecology at the University of North
Carolina at Chapel Hill School of Medicine, and a principal investigator for
the U.S. trials.
At the Congress, researchers reported the pooled results for 1,378
premenopausal women, average age 35, who took 100 milligrams of the drug or a
placebo pill during a 24-week period. The trials were in Europe and North
America. The women kept track of the number of satisfying sexual encounters --
defined as intercourse, oral sex, masturbation, or genital caressing by their
partners. All women had to be in a stable, monogamous relationship. All women
had a diagnosis of hypoactive sexual desire disorder (HSDD), marked by a
decrease or absence of sexual desire accompanied by distress in the
When researchers compared sexual desire and events during the last four
weeks to the first four weeks, they found that those on the medication went
from 2.8 sexually satisfying events in the first four weeks to 4.5 in the final
four weeks. Those on placebo went from 2.7 to 3.7.
''The difference was [about] one additional satisfying sexual encounter a
month," says Thorp.
The study also shows the drug improved sexual functioning and distress
related to the sexual problems.
About 15% of the women taking the medication dropped out due to adverse
events, according to information from Boehringer Ingelheim Pharmaceuticals,
which makes the medications, while 7% of women on placebo discontinued the
study. Among the most commonly reported side effects were daytime sleepiness,
dizziness, anxiety, and fatigue.
Exactly how flibanserin improves sexual desire isn't known for sure. "We
think it modulates neurotransmitters involved in sexual functioning," says
Michael Sand, PhD, MPH, director of clinical research and team leader,
flibanserin, for Boehringer Ingelheim.
''It interacts with [neurotransmitters] serotonin and dopamine in the
central nervous system," Thorp says.
Originally studied as an antidepressant by Boehringer Ingelheim, the drug
didn't prove effective for depression. But when researchers noticed reports of
improved sexual desire in some participants, the research changed focus.
As for critics, Thorp acknowledges that ''there are multiple criticisms [of
the studies] that are justifiable. One is the whole measurement issue and how
do you quantify an objective response? That's particularly hard when the
disorder is subjective."
He notes, too, that the placebo group also saw improvement. "There was a big
placebo effect,'' he says, noting that attention from a concerned doctor may
also contribute to improvement in the sexual functioning of women with
"The data look good," says Kathleen Segraves, PhD, associate professor of
psychiatry at Case Western Reserve University in Cleveland and a sex
therapist who reviewed the data for WebMD. "But only clinical experience and
actual practice will reveal how clinically useful the effect is."
Case Western Reserve was one of the U.S. study sites for flibanserin, but
Segraves 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, and
perhaps 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 the
desire of a man. It may give him more confidence. It gives him a reliable
erection. It inflates the penis. He still needs to have desire."
The differences in the number of satisfying sexual encounters may seem
small, Segraves says. But it would probably not be considered small by the
women who have the condition, she says.
"You have to remember these women have lost desire over time and for some
time. You have to remember these women [with no sexual desire] are very
distressed by it. If you go from zero to one, you're pleased as punch, because
you were flat-lining before."
Some wonder if developing a pharmaceutical for women’s lagging desire is
more about business than pleasure. "We need to address multiple factors that
underlie sexual desire," says Gina Ogden, PhD, a sex therapist in Cambridge,
Mass., and author of The Return of Desire. Of the development of
flibanserin, she says: "I think the focus is more to line the pockets of the
pharmaceutical companies than to address the real and multiple factors involved
in women's sexual desire." A woman's desire, says Ogden, is influenced by many
factors, including her feelings about sex, what sex means to her, and what
types of intimacy she prefers.
Boehringer Ingelheim is continuing studies. Recruitment of both
premenopausal and postmenopausal women with HSDD for new clinical trials is
beginning, Sand says.
He wouldn't comment on a possible timeline of when the drugmaker might ask
for FDA approval or when it may be on the market.
SOURCES:John M. Thorp Jr., MD, McAllister distinguished professor of obstetrics and
gynecology, University of North Carolina at Chapel Hill School of Medicine.Kathleen Segraves, PhD, associate professor of psychiatry, Case Western
Reserve University, Cleveland; sex therapist.Michael Sand, PhD, MPH, director, clinical research and team leader,
flibanserin,Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, Conn.Gina Ogden, PhD, sex therapist; author, The Return of
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