The first prescription drug to enhance women’s sexual drive won regulatory approval Tuesday, clinching a victory for a lobbying campaign that had accused the Food and Drug Administration of gender bias for ignoring the sexual needs of women.

The drug — Addyi from Sprout Pharmaceuticals — is actually the first drug approved to treat a flagging or absent libido for either sex. Viagra and other drugs available for men are approved to help achieve erections, or to treat certain deficiencies of the hormone testosterone, not to increase desire.

Advocates who pressed for approval of Addyi, many of them part of a coalition called Even the Score, said that a drug to improve women’s sex lives was long overdue, given the many options available to men.

“This is the biggest breakthrough for women’s sexual health since the pill,” said Sally Greenberg, executive director of the National Consumers League.

But critics said the campaign behind Addyi had made a mockery of the system that regulates pharmaceuticals and had co-opted the women’s movement to pressure the FDA into approving a drug that was at best minimally effective and could cause side effects like low blood pressure, fainting, nausea, dizziness and sleepiness.

In announcing the approval, Dr. Janet Woodcock, a senior FDA official, said the agency was “committed to supporting the development of safe and effective treatments for female sexual dysfunction.”

The FDA decision Tuesday was not a surprise since an advisory committee of outside experts had recommended by a vote of 18 to 6 in June that the drug be approved, albeit with precautions required to try to limit the risks and ensure that it was not overused.

The big question now is how many women will use Addyi, which is also known as flibanserin and has been called the “pink Viagra.”

According to one survey, about 10 percent of women suffer from hypoactive sexual desire disorder.

Cindy Whitehead, the chief executive of Sprout, declined to predict sales of Addyi, which she said would be available starting Oct. 17.