It’s the sort of fantasy once confined to ads in back pages of girly magazines: an aphrodisiac that renders even the clumsiest, onion-breathed lover irresistible to women. Charlatans have sold such love potions to the gullible for thousands of years. But with the success of Viagra, claims like this carry with them a new kernel of credibility.

 

Scientists are, in fact, working hard on chemicals to stoke women’s sexual fires. Already some compounds have been shown in placebo-controlled, randomized clinical trials to stimulate measurable effects: blood flow to the genitals, even increased attempts to initiate sex. While “pheromone cologne” may be of dubious efficacy, at least two drugs purported to boost women’s sex drive in novel ways are expected to reach the market in the next few years. One comes from German pharmaceutical company Boehringer Ingelheim and the other from Palatin, a Cranbury, New Jersey-based startup; both are in clinical trials.

 

The potential market for any drug that wins approval from the U.S. Food and Drug Administration is huge. Worldwide sales of Viagra have topped $1.6 billion for each of the past three years. And the potential for a drug designed specifically for women could be even larger: in a 1999 survey reported in JAMA, The Journal of the American Medical Association, 43 percent of women experienced some sort of “sexual dysfunction” compared to 31 percent of men.

 

The only FDA-approved sex drugs on the market are sildenafil, the active ingredient in Viagra, and related compounds for treatment of erectile dysfunction in men. Some physicians are prescribing them for women, yet Pfizer, which makes Viagra, has apparently abandoned its campaign to have the drug approved for women. Why? Trials showed that for many women, getting a clitoral erection isn’t the same thing as being in the mood for love. To veterans of sexual medicine, that’s no surprise. “You don’t just give someone a pill and it turns everything on,” says Dr. Andre Guay, a Harvard University assistant professor who directs the Sexual Function/Endocrinology Clinic in Peabody, Massachusetts. 

 

So far, the medical options to help women unhappy with their sex lives are limited. Testosterone is a top choice; in one study, women wearing a skin patch containing this male hormone had sex once a month more often than women wearing a placebo patch, and overall reported happier sex lives. But the FDA nixed the patch, marketed abroad by Procter and Gamble as Intrinsa, because of questions about long-term health risks.

 

Dr. Guay is also prescribing dehydroepiandrosterone, a precursor to testosterone, available over-the-counter under the name DHEA. But here the research is even more preliminary, and the leading association of hormone specialists, the Endocrine Society, has recommended against treating women with any male hormones or precursors.

 

These disappointments have added to the buzz about two other chemicals working their way through the approval pipeline: flibanserin, designed by Boehringer Ingelheim, and bremelanotide (originally dubbed PT-141), created by Palatin. Both have shown promise in Phase II clinical trials. Unlike Viagra and its cousins, these drugs don’t just engorge the genitals—they appear to increase desire for sex by acting on the brain. Flibanserin stimulates receptors for two neurotransmitters, serotonin and dopamine. Many antidepressants also work on these neurotransmitters, and researchers were originally testing flibanserin as an antidepressant when they discovered that it was arousing some test subjects. Bremelanotide stimulates receptors for the hormone melanocortin, which as its name implies is also involved in skin color. Researchers were testing a related compound as a tanning agent when their patients suddenly developed erections, giving the scientists their eureka moment.

 

In trials of bremelanotide, which is inhaled as a nasal spray, a few women experienced nausea, but the majority said they got turned on, and some initiated sex for the first time, according to the company. “It creates a better sensitization to touch and increases the ability to be aroused,” says Palatin CEO Carl Spana, who predicts the drug will be approved within three years for men and soon after for women. Much of the company’s hopes depend on this molecule; Palatin is not yet profitable, having scored scant success with the diagnostic products it tried in the 1990s. Boehringer Ingelheim, by contrast, is well established, with 2006 revenues of $14 billion driven by successful respiratory and cardiovascular drugs. Officials there have little to say about flibanserin except that they expect results of Phase III trials in women in 2008.

 

Not everyone is excited. “These drugs … are all unlikely to benefit women,” says Leonore Tiefer, a clinical associate professor of psychiatry at New York University. “They’re being promoted in a way that will either make people think they have a problem when they don’t, or that the drugs will enhance their experience when they won’t.” Even endocrinologists like Dr. Guay acknowledge that counseling is at least as important as drugs, depending on the needs of the patient.

 

So, will there ever be such a thing as an aphrodisiac for women? Perhaps, but it probably won’t be something a lonely guy can spray on his shirt. Drugs might work for some women, while other women may need time to relax, better information about sex—or a lover with clean teeth who knows how to dance.