Nov. 5, 2008 -- Low sexual desire is a common complaint among women, but there is no drug treatment specifically approved for the problem.
But questions remain about the treatment's safety.
An increasing number of women in the United States have been using testosterone off-label to treat problems with sexual desire, arousal, and achieving orgasm.
The new study examined the safety and effectiveness of an experimental testosterone patch developed specifically for the treatment of low sexual desire in women. The study was paid for by Proctor & Gamble Pharmaceuticals.
Testosterone Patch Revisited
The company sought fast-track approval for a 300-microgram patch, which it calls Intrinsa, in 2004, specifically for women who had had declines in testosterone levels as a result of having surgically induced menopause.
But in December of that year, a 14-member FDA advisory committee unanimously rejected the request, citing concerns about the lack of long-term safety data and off-label use.
The new study included women who had undergone surgically induced menopause and women who had undergone menopause naturally, all of whom were diagnosed with low sexual desire.
The 52-week study included 814 women with sexual desire disorder, characterized by troublesome low sexual desire or function.
About a third of the women wore patches delivering 300 micrograms of testosterone per day, another third wore 150 microgram patches, and the rest of the women wore placebo patches with no testosterone.
More Satisfying Sex
The women were asked to keep sexual encounter diaries, and researchers used other established measures to assess sexual response during the six-month evaluation phase of the study.
They found that compared to placebo users, the women who used the 300 microgram patch reported significant improvements in sexual functioning, including desire, arousal, orgasm, and pleasure. This was not the case for women who wore the lower-dose testosterone patch.
Women who wore the higher dose patch had about two more satisfying sexual experiences over a four-week period than women in the placebo group. Women in the lower-dose group had one more.
At the start of the study, about half of all sexual episodes were rated as satisfying. By week 24, 78% of the episodes in the higher-dose testosterone group were rated as satisfying, compared with 65% in the placebo group.
Lead researcher Susan R. Davis, MD, PhD, tells WebMD that the findings show that testosterone is an effective treatment for low sexual desire in women without adding estrogen treatment to the mix.
"Unlike men, women tend to continue to have sex even when it is not particularly satisfying for them," she says. "So if they are having sex five times a month on average and they can enjoy it twice as often, that could make a big difference."
4 Breast Cancers Found
Women in the higher-dose testosterone group reported a slight increase in facial hair, but they did not find this troubling enough to stop taking the hormone, Davis says.
"Considering that most women will only end up using testosterone for a couple of years, it is probably safe," she says.
But Julia R. Heiman, PhD, who directs the Kinsey Institute for Sex, Gender and Reproduction, isn't so sure.
"I think very important questions remain about the safety of this treatment in light of this finding," she tells WebMD.
Heiman says there is a clear need for better ways to address sexual desire issues in women, especially because so many women now take antidepressants and other drugs that can cause sexual problems.
But in an editorial published with the study, Heiman urged caution in using testosterone for low libido "until we understand more about its possible link with breast cancer and are better able to predict which patients are more likely to be subject to negative effects."
A spokesman for Procter & Gamble Pharmaceuticals would not say if the company will seek FDA approval for its testosterone patch developed for women.
"We continue to work with the FDA to determine if there is an appropriate pathway forward for Intrinsa, but beyond that we are not providing comment," Tom Millikin tells WebMD.