Why There's (Still) No Viagra for Women
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The first "female Viagra" drug touted as boosting women's sexual desire could be approved today, assuming the Food and Drug Administration decides it's safe and effective.

But the odds don't look good, as the FDA has already rejected the drug, called flibanserin, twice.

Although some organizations say that sexism is playing a role in the drug's lack of approval, experts say safety is the main criterion underlying the agency's rejections so far.

And even if flibanserin does get approved, it's unlikely to work the same magic on a couple's sex life as Viagra, said two experts, Dr. Mary Jane Minkin, a clinical professor of obstetrics and gynecology at Yale University School of Medicine in New Haven, Connecticut, and Dr. Elizabeth Kavaler, a urologist at Lenox Hill Hospital in New York City.

That's because flibanserin targets sexual desire, a much more complicated issue than the mechanics of performance, both Minkin and Kavaler said.

What's more, scientists haven't clearly defined how low a person's sex drive needs to dip for it to be considered a disorder, they said. [Hypersex to Hoarding: 7 New Psychological Disorders]

Sexism or safety?

Several feminist organizations have pointed out that 26 drugs are now marketed for men with sexual dysfunction, and not a single one has been approved for women. They argue that the FDA has repeatedly rejected flibanserin's drug approval application because of a sexist belief that women aren't supposed to want or need sex.

But those numbers are misleading, Minkin said, because there are only a few active ingredients in the many drugs for men. In addition, there are several drugs now in late-stage trials that target low sex drive in women. For instance, the drugs Lybridos and Lybrido, made by the company Emotional Brain, combine testosterone with either sildenafil, the active ingredient in Viagra; or BuSpar, an anti-anxiety drug, with the aim of treating women with low libido.

The real issue for the FDA is not sexism, Minkin said, but whether the drug works safely. Sprout Pharmaceuticals, which makes flibanserin, has not yet adequately demonstrated that the drug is both safe and effective, she said.

"The data they brought last time did not seem appropriate to lead to the approval of the drug," Minkin said.

Flibanserin is thought to boost libido by altering levels of brain chemicals such as dopamine and serotonin, which are known to play a role in feelings of desire, motivation, appetite and satiety.

But it is far from a miracle pill. In past trials, premenopausal women who took the drug reported, on average, gaining less than one additional pleasurable sexual experience per month, and some experienced side effects such as nausea, dizziness and drowsiness, Minkin said.

And unlike Viagra, which is taken only when someone wants to have sex, flibanserin must be taken daily, raising the risk of long-term side effects, according to a letter of concern sent by several women's health organizations to the FDA last April.

The need to take the drug daily is what "raises toxicological concerns that make it appropriate for the FDA to subject flibanserin to elevated safety scrutiny," the letter said. In the early trials of the drug, there were  reports of substantial side effects, and some women dropped out of the trials, according to the letter.

Vague diagnosis

On top of that, there isn't really a clear way for doctors to decide whether a person's level of desire is normal, or needs fixing, Kavaler said. And without a clear measure of the drug's effectiveness, the FDA must base its decision solely on safety, she said.

"All you can measure is safety, and so you better have a safety profile that's pretty much like taking a sugar pill," Kavaler told Live Science.

It's possible that, today (June 4), Sprout Pharmaceuticals will produce new safety and effectiveness data that could tip the FDA in its favor, Minkin said.

Desire versus performance

Even the comparison between Viagra and flibanserin is faulty, Minkin said.

"They're very different drugs," Minkin told Live Science.

Viagra helps men who already want to have sex actually do so, by increasing blood flow to the penis, Minkin said. In contrast, flibanserin targets premenopausal women who are physically able to have pain-free and pleasurable sex but are never in the mood, Minkin said.

Spurring any kind of desire with just a pill is tricky, Kavaler said.

"How do you make somebody want to have sex? How do you make someone want to go to work in the morning? I don't know how a pill does that, because there are so many aspects to desire," Kavaler told Live Science.

In addition, waning sexual desire may be normal for people in certain life stages, Kavaler said.

"Why is it that divorced women who date are interested in sex, or young women who date are interested in sex, but you can take a 35-year-old who's got two kids — why would she want to have sex? She wants to go to sleep."

Minkin noted that drugs like flibanserin are being developed because many women with low libidos perceive their lack of desire as a serious problem.

What's really sexist is framing the issue of low sexual desire as just a woman's problem, Kavaler said.

"Plenty of women complain that their husbands are totally not interested" in sex, she said.

Follow Tia Ghose on Twitterand Google+. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.