FDA approves "female Viagra": How does flibanserin work?

Did the FDA Really Just Approve the “Female Viagra”? Not So Fast.

Did the FDA Really Just Approve the “Female Viagra”? Not So Fast.

The XX Factor
What Women Really Think
June 5 2015 5:18 PM

The New “Female Viagra” Works Not on the Genitals, But on the Brain

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Coming soon to a pharmaceutical ad near you.

Tony Bowler/Shutterstock

When it comes to addressing sexual dysfunction, men have no shortage of options. For women, alas, there are none. True, there have been a few half-hearted attempts to address the problem: Doctors have occasionally prescribed estrogen pills and creams, and some European countries have briefly experimented with testosterone patches before taking them off the market. But, for the most part, women’s lack of desire—or hypoactive sexual desire disorder (HSDD)—remains an “unmet medical need.” Enter flibanserin, the pill that gives you back your sex drive. Finally, the Female Viagra!

This at least is the argument put forth by Even the Score, a coalition of women’s groups including the National Council of Women’s Organizations and the American Sexual Health Association. (The argument is further summed up in this fairly hilarious parody Viagra ad.) The coalition is working with the drug’s developer, Sprout Pharmaceuticals, to bring this libido-in-a-pill to the masses. Looks like it worked: On Thursday, the FDA advisory committee voted 18-6 to recommend approval of flibanserin. It was a surprising about-face, given that the FDA had previously rejected the drug—twice—for failing to prove that its results justified its risks, which include fainting, low blood pressure, and drowsiness.

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Alas, notwithstanding any risks, this is not Viagra for women. Viagra is an impotence aid used to treat erectile dysfunction. It relies on a simple physical mechanism for a simple physical problem: It sends more blood to the penis to keep it erect. Viagra assumes that sexual drive is present, just not physical ability. In fact, neither men nor women have ever had a pill that does what flibanserin purports to do, which is to address something trickier and altogether more vague: the locus of sexual desire.

Flibanserin works not on the genitals, but on the brain. In fact, the pill was originally developed to treat depression; researchers initially feared it would hurt, not promote, sexual desire. Flibanserin is what's known as a 5HT1A agonist and a 5HT2A antagonist; it shares mechanisms in common with the antidepressant and anti-anxiety drug buspirone (Buspar).* As a 5HT1A agonist, it promotes dopamine release. But nobody’s really sure exactly how it elevates lust. “Flibanserin’s mechanism in the treatment of HSDD is unknown,” according to the FDA briefing.

We have a tendency to want to swallow a pill and be done with it. But unlike an erection, sexual desire is a mysterious, many-layered thing. Is it really a good idea to medicate it with a pill whose effects you can’t even explain chemically? “Sexual response is a delicate dance between multiple neurotransmitters,” as Andrew Thomson, a psychologist at the University of Virginia who has researched the side effects of antidepressants on sexuality and romantic love, puts it. “Whereas with Viagra, you just engorge the penis with blood.” A more accurate female equivalent to Viagra, Thomson says, would be “a drug that has a direct response on the clitoris.”

*Correction, June 6, 2015: This post originally misstated that flibanserin is a selective serotonin reuptake inhibitor (SSRI). It is in fact a 5HT1A agonist and a 5HT2A antagonist. 

Rachel E. Gross is the science web editor at Smithsonian.