“We had sex five times a week when before it was once a week,” Zita told me shortly after she’d finished her supply of Lybrido. And she wasn’t enthusiastic about that weekly intimacy. With the drug, she said, “I wanted to have sex even after we had sex. I would feel horny, and I got like a throbbing sensation, like I had to do something or it was going to bother me all night. I would just want more.” When I asked how her husband felt about her taking the medication, she laughed."Happy,” she said.

Tuiten published some results from small, preliminary trials in the March issue of The Journal of Sexual Medicine. His full data, which he has just finished tabulating and will soon be taking to the F.D.A., show Lybrido bestowing unmistakable benefits in desire — and in rates of orgasm. (The outcomes for Lybridos aren’t thoroughly compiled, but he says that early results look about as positive.) Tuiten is confident that the F.D.A. will send him to do another larger set of trials, which will involve about 1,200 subjects. Plenty of drugs fail at that stage of replication. But if all goes well, by 2016, Lybrido and Lybridos might be on the market.

Is it possible, after all, that through the pharmaceutical industry a fairy-tale ending could come to pass? Perhaps the fantasy that so many of us harbor, consciously or not, in the early days of our relationships, that we have found a soul mate who will offer us both security and passion, till death do us part, will soon be available with the aid of a pill.

But of course swallowing a tablet can take us only so far. Chemically enhancing a woman’s desire might play out in all kinds of ways within a relationship. Some couples might feel closer, others might feel desolate because, despite more sex, their bond isn’t stronger. Wives might yearn for the old seductive efforts of their husbands, even if those gestures stopped working long ago. Women might feel yet more pressure to perform: Why not get that prescription? their partners might ask; why not take that pill? And men, if they are willing to confront the truth, might not be so happy about the reminder, as their partners reach for the pill bottle, that their women need chemical assistance to want them. All the agonies that have existed since the dawn of monogamy will still pertain, many of them coming down to the craving to feel special.

Beyond what might happen in millions of bedrooms, it’s even more difficult to foresee what societal transformations might be stirred. Just as with the birth-control pill, a foreboding not only about sex itself but also about female empowerment may be expressed in a dread of women’s sexual anarchy. Over the last decade, as companies chased after an effective chemical, there was fretting within the drug industry: what if, in trials, a medicine proved too effective? More than one adviser to the industry told me that companies worried about the prospect that their study results would be too strong, that the F.D.A. would reject an application out of concern that a chemical would lead to female excesses, crazed binges of infidelity, societal splintering.

“You want your effects to be good but not too good,” Andrew Goldstein, who is conducting the study in Washington, told me. “There was a lot of discussion about it by the experts in the room,” he said, recalling his involvement with the development of Flibanserin, “the need to show that you’re not turning women into nymphomaniacs.” He was still a bit stunned by the entrenched mores that lay within what he’d heard. “There’s a bias against — a fear of creating the sexually aggressive woman.”

Gaining control of their reproduction in the ‘60s affected not just women’s sex lives but also everything from their social standing to economic empowerment. What might it mean for conventional structures if women could control, with a prescription, the most primal urge? So many things, personal and cultural, might need to be recalibrated and renegotiated, explicitly or without acknowledgment. The cumulative effect of all those negotiations could be hugely transformative, in ways either thrilling or threatening, depending on your point of view.