On June 18, an FDA advisory committee will meet to consider recommending a drug that promises to treat low libido in women. Originally developed as a potential antidepressant, flibanseren appears to reduce levels of the neurotransmitter serotonin but boost amounts of two other brain chemicals. MORE asked Nanette Santoro, MD, vice-president of clinical science for The Endocrine Society, if a lack of interest in sex is really a problem for women—and whether drugs might be the best cure.
Q: How much of an issue is low libido for women?
A. It’s a relatively prevalent complaint. In studies, about 40 to 60% of women will report a sexual problem, and the most common one is low sex drive. A recent study by Jan Shifren at Massachusetts General says women are more likely to feel distress from experiencing low desire than from other sexual problems. But that doesn’t mean that every woman with a weak sex drive is troubled. In this study, women aged 45 to 64 were more likely to be bothered than younger women. They may have been having consistent sex and then their sexual activity started to drop off. These are women doctors might be able to treat.
Q: What do you think is the main cause of a low interest in sex?
A. When you look at larger studies, far and away the dominant factor is relationship issues. So in many cases, there is some kind of relationship problem that is showing up as a sex issue.
Q: To what extent do physical factors play a role?
A: There are physiological changes in sexual response over time, and that is not always a welcome thing. According to the researchers Masters and Johnson, your sexual peak is at age 35 and after that, it’s downhill. With menopause comes changes in the vaginal tissue that make it more fragile; women are more susceptible to vaginal dryness, and the tissue may become less elastic. That may make sex less satisfying and more painful. But those issues are very readily addressed with hormonal treatments. Estrogen, which is usually given vaginally for these types of concerns, will restore the vaginal tissues and relieve the problems that women may have with lubrication.
Doctors also need to consider what medications women are using. For example, SSRIs [antidepressants like Prozac that affect serotonin and other neurotransmitters] can cause an inability to have orgasms or a complete loss of interest in sex.
Q: How is a lack of sexual interest generally treated?
A: If there are relationship difficulties, often a referral to a sex therapist will help. In cases where low estrogen or menopause are the issue, adding low doses of estrogen is helpful and will relieve vaginal symptoms. Testosterone has been recommended and discussed, but it has not been FDA-approved for use in this country. Women do take it off-label and get some benefit from it, especially women who have had their ovaries removed. Everyone’s looking for a panacea, and testosterone tends to get a lot of the hype. But as most sex therapists will tell you, the most important sex organ is the brain, and that may be where the motivation—or lack of motivation—lies.
Q: How do you treat libido issues?
A: I tend to avoid off-label methods. The Endocrine Society has come out with a position statement recommending against using testosterone with most women, because we really don’t know the potential side effects. Typically, I will look for relationship issues, and more often than not, that is what I find. Issues may have been brewing for some time; the physiological factors may collide with a relationship issue that has been steadily getting worse. If we can identify that chronic issue, coping with a woman’s own physical problem becomes much easier.
Q: What is the mechanism behind flibanserin?
A: That name sounds like a volcano in Iceland, doesn’t it? In any case, it’s not really clear. For those of us who have seen how sexual interest can be switched off like a light bulb with an SSRI, this drug is very intriguing; it may be operating the other way around to kindle interest.
Q: Boehringer-Ingelheim says it intends to initially market flibanserin to pre-menopausal women. Why?
A: Probably because the drug was tested on them. The data are often clearer on younger women. Post-menopausal women are trickier, because they have specific hormonal issues to contend with as well. Once the drug is approved it may be used off-label in postmenopausal women.
Q: What effect do you think flibanserin will have on relationships?
A: I think women are going to take it more in the context of a long relationship than in a new relationship. People usually come in for treatment of low libido because they feel mismatched with their partner over time. This is more of a “bring-her-back-to-restore-the-harmony-in-our-relationship” kind of thing, and the drug may serve that purpose for some couples. If there’s a relationship problem that goes unaddressed, however, clearly the pill isn’t going to work, and you’d be treating the wrong thing.
Q: Flibanserin does not have a huge impact on sexual activity. Do you think it is still worth taking?
A: The size of the effect is very important. Drug researchers found that flibanserin added just one episode of sexual improvement per month. This is not huge. If couples are having sex once a week or more, the effect of the drug is unlikely to be a major factor in their sex lives, which is why it’s important that women understand how much this is likely to do for them. I think women are perfectly capable of doing the math for themselves. Once flibanserin is out there, women will need to know what they should expect.
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