Not So Fast

The Society concluded that the most common current treatment, testosterone, should not be recommended. The big question: If a woman doesn't experience physical desire, is it a medical condition, like inadequate blood flow in men, or something purely psychological? "Maybe she just doesn't like the guy she's with," says Washington (D.C.) psychotherapist David Waldman.

Plus, it's not yet clear exactly how flibanserin works. Company researchers have figured out that it hits several circuits in the brain that are linked to feelings and pleasure. One of those circuits apparently helps control sexual desire and arousal, although the effects are not immediate. "This is not something that can be taken on a Friday for the weekend," says Boehringer Ingelheim spokesman Mark R. Vincent. "There is a gradual increase in sexual desire over a six- to eight-week period."

Pinning down the mechanism is especially critical, in this case, because the FDA views drugs that affect the complicated central nervous system with extra caution. Regulators are especially wary of drugs that might be used widely as a lifestyle choice rather than just to treat disease. "It is difficult for drugs for the central nervous system to be approved for something as banal as sexual function," says Lahey Clinic's Guay.

Doctors investigating new treatments for women retort that men's problems were also seen as largely psychological until Viagra came along, and that loss of sexual desire isn't trivial to many of those who experience it. Indeed, Boehringer says it's having no trouble recruiting women for the trial, some of whom travel long distances for the chance to try the drug. Even if flibanserin doesn't pan out, understanding how it boosts desire should point the way to better versions—and perhaps give women a choice about whether or not to pop a little pill.