The dream of a pill to treat a lack of sexual desire in women has moved closer to reality after U.S. government advisers recommended the approval of flibanserin, a controversial drug that the U.S. Food and Drug Administration has rejected twice since 2010.

A panel of FDA advisers voted 18 to six Thursday in favour of approving the drug, though all of those who voted yes said approval should come only if certain measures are taken to reduce the risk of side effects – setting the stage for a pitched battle before the FDA makes its official decision in August.

"I'm just really concerned about the advisory committee approving this," said Vancouver counsellor and sex therapist David McKenzie on Thursday. "Because it puts more pressure now on women, probably from male partners, to step up to the plate. And it's just not right – it just doesn't work that way."

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Mr. McKenzie and other critics argue that female sexuality is too complex to be addressed with a pill and add that flibanserin poses too many health risks – and would provide too little benefit – to merit FDA approval.

The drug's manufacturer, however, says it is pursuing a "much-needed scientific and societal breakthrough for women" and, along with other drug makers, maintains the FDA has unfairly overlooked therapies for women while approving several erectile dysfunction drugs for men.

Dr. Lori Brotto, director of the sexual health laboratory at the University of British Columbia, said she was "on the fence" about the drug, saying a small group of women might benefit from it but adding that she shares concerns about the oversimplification of desire disorders and the potential side effects of the drug.

Flibanserin, a pink pill that would be taken every day at bedtime, would be approved to treat a lack of sexual desire in premenopausal women that cannot be attributed to disease or other known causes. Sprout Pharmaceuticals, which owns flibanserin, says 7 per cent of premenopausal women have this condition, known as hypoactive sexual desire disorder.

Flibanserin has already been rejected twice by the FDA, which said the drug's minimal benefits did not outweigh its risks. The first rejection, in 2010, came after an advisory committee similar to the one that met Thursday recommended unanimously to not approve the drug.

After the second rejection, in 2013, some women's groups brought together by a consultant to Sprout organized a campaign to press the FDA into approving the drug. The campaign, Even the Score, accused the agency of gender bias because it had approved Viagra and other drugs to help men have sex while leaving women without options.

Other women's groups and individuals countered that Sprout and its allies were using women's rights as a cover to force the approval of an undeserving drug.

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Three clinical trials testing flibanserin were consistent in their results. The women who took part were having an average of two or three "sexually satisfying events" per month when the studies began; once they started taking the drug, the number of such events increased – by about one event more per month than for women in the trial who got a placebo.

Women getting flibanserin also reported on monthly questionnaires that they felt more desire, though the difference with a placebo was about 0.3 points on a scale ranging from 1.2 to 6.0.

The side effects of most concern to the FDA were low blood pressure and fainting. While these were rare in the clinical trials, they seemed to raise the risk of accidental injury, with one woman suffering a concussion when she fell.

Moreover, the risk of such side effects increased when the women drank alcohol or took certain other medications, like the antifungal drug fluconazole, which is used to treat vaginal yeast infections, and birth control pills. Much of the discussion in Thursday's meeting dealt with reducing those risks, perhaps by requiring that women taking the drug refrain from drinking alcohol.

Supporters of the drug said a failure to approve it would discourage the pharmaceutical industry from pursuing treatments for female sexual disorders and that the lack of an approved medicine would only cause women to use other drugs off label or to seek help from dubious supplements hawked on the Internet.

Several speakers opposed approval. Dr. Adriane J. Fugh-Berman, director of a project at Georgetown University, called flibanserin "a mediocre aphrodisiac with scary side effects." She said the clinical trials were restricted to healthy women, but that if approved the drug would be used by a wider range of women, resulting in "an epidemic of adverse events."

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She also said the FDA should resist the Even the Score campaign.

"To approve this drug will set the worst kind of precedent – that companies that spend enough money can force the FDA to approve useless or dangerous drugs."

It is inaccurate to suggest there is nothing on the market to treat a lack of sexual desire, Dr. Brotto said, adding that behaviour therapy and other approaches can help.

"There is evidence to support those things – they're just not medication," Dr. Brotto said.

"I hope [the FDA] will override the recommendation of the advisory committee and say that this is the wrong drug, for the right reason," said Leonore Tiefer, an associate professor of psychiatry at the New York University School of Medicine and founder of the New View Campaign, which opposes flibanserin.

"Yes, we want something for doctors [treating women who report having low sexual desire]. Yes we want something for patients. But this is not a good drug," Dr. Tiefer said.

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With a report from The New York Times News Service