Image from Cosmopolitan
Image from Cosmopolitan

Lack of sexual desire is one of the most common sexual problems for women. While men who have sexual dysfunction issues (low libido or erectile dysfunction) have big Pharma to turn to, women do not.

In 2010 Boehringer submitted an application to get their “women’s Viagra,” flibanserin, approved and were denied. The FDA cited efficacy and side effects. Some claim that was sexist as the men’s sexual pharmacopeia seems to be ever-expanding (although that testosterone doesn’t exactly seem to be so safe), although of the studies submitted only two were deemed good enough for full review (having read the studies, I agree) and even then these studies didn’t even prove one of their co-end points (one end point was more sex, the other was more desire). Seeing that the desire thing didn’t work out so well the company tried to say they used the wrong scale, but that’s the kind of thing that gets the FDA worked up. You can’t say you’re going to use one scale and when it doesn’t work out claim that back up scale you used, yeah, that was really the better one all along. Sigh.

The end results of the first two studies that the FDA felt were acceptable are as follows (where SSE = satisfying sexual events):


Basically, about 30-40% of women who took flibanserin responded versus 15-30% for placebo takers. Overall, there was increase in 1-1.8 number of satisfying sexual encounters a month. Whether the FDA is  easier on sex drugs for men I don’t know, but failing to approve flibanserin the first go round was correct. You need more than 2 studies especially if you haven’t proven one of your two primary end points (desire).

Sprout is re-submitting flibanserin to the FDA and there are a couple of more studies to look at. They seem to have fixed the whole desire issue (they changed the scale in the studies, whether that’s designing a scale to find and end point or a truly valid sexual desire scale I’m not entirely sure). The studies report an increase in desire using this FSFI desire score that is statistically significant, but I don’t know how that translates into real world as only one study reported if the women felt the increase was meaningful.


The bottom line from a how much more sex am I really going to have point of view is once more a month with flibanserin versus placebo, but many women are not responders. While this may be statistically significant, it remains to be seen whether women consider it a meaningful change.

It is hard to know what to make of the desire scale. According to the people who came up with it (i.e. researchers who study these drugs on women) this is a meaningful way to measure the effect of medications on desire (although the cynic in me wonders if this is designing a scale to find your desired end point rather than simply a measurement). The newer studies indicate there is statistically significant increase on this desire scale with flibanserin.

Don’t get me wrong, desire/felling desirous is an important outcome measure! Not feeling desirous can be emotionally difficult and it is possible that increasing desire might lead to more masturbation (interestingly none of the studies looked at that, I mean why does sex with someone else have to be the end point?). The point of drugs for erectile dysfunction is an erection strong enough for penetration, not the number of acts of penetration. A man with erectile dysfunction who has no partner might still want to have erections and I’m ok with that. Desire is a great end point, but I do think both women and clinicians might like a real world translation, as in what will this mean for me. How do I translate this desire scale into my care of women?

What about safety concerns/side effects? Flibanserin has a lengthy list of drug interactions and a moderate adverse effect profile. Many women were excluded from study based on other medications and/or medical conditions, so who exactly can take this drug safely right now seems to be healthy women with almost no medical conditions on almost no medications. Flibanserin also causes breast tumors in mice in relatively low doses (a concern), but not in rats. This could be a species specific thing and may not applicable for humans, but given studies have only been following women for a year it’s hard to know. The dose that gave tumors to the mice was relatively low, so, yeah. I’d sure like to see more on that.

So that’s a review of flibanserin. Any claims it was rejected by the FDA based on discrimination of products for women are bogus. Two studies that don’t prove one of your stated endpoints is an issue. We’ll see if it passes the FDA using this different desire scale.

That being said, would you take a drug every day if the end point was one more episode of sex a month?

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  1. Something I have wondered about this drug: Since many women gain no benefit it suggests to me that the average is not a reasonable way to measure the benefit. The average of a double-humped curve (one for those who benefit, the other at zero) doesn’t tell you much about the humps.

    1. The baseline # of sex encounters in the studies were about 2 a month, so I do think studies looking at lower frequency of sex at baseline are important. Going from 4 encounters a year to 12 is different than going from 24 to 36. Thanks for your input!

  2. I’ve tried switching around birth control, ArginMax and some other supplements to boost sex drive and have not felt any changes. I have vaginismus which has seriously damaged my sex drive. Do you know of anything natural that people have had success with?

  3. Excellent summary of the issues and hocus pocus in the efficacy studies. Your commonsense statements trump the biostatistical nonsense that comes out of the FDA and the Big Pharma.

  4. Thanks for your thoughts on this. It’s disheartening to see organizations like NOW and ISSWSH and ASHA give their wholehearted support based on such flimsy evidence. And why is no one else talking about the carcinogenic effects in mice???? Instead of asking the FDA to lower its standards for women’s health drugs, we should be demanding better scrutiny of all new meds put to market!

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