An activist group has launched a campaign to get the federal Food and Drug Administration to approve flibanserin, also known as the female Viagra. Even the Score has gathered more than 55,000 signatures for its online petition urging acting FDA Commissioner Stephen Ostroff to allow the pink pill to come to the market.

The petition claims the lack of libido-enhancing drugs for women reflects “persistent gender inequality” at the FDA. In contrast, there are 26 government-approved drugs to treat sexual dysfunction in men. FDA advisers will decide Thursday whether to approve flibanserin.

So what exactly is flibanserin, and how does it work? Sprout Pharmaceuticals is behind the pill, which has been endorsed by 17 women’s and health organizations. Critics, however, claim there is no proof that flibanserin is actually an antidote to hypoactive sexual desire disorder (HSDD), which can cause women to lose their desire for sex.

The drug increases the effects of desire-enhancing chemicals like dopamine and decreases the impact of inhibitors like serotonin, Sprout Pharmaceuticals CEO Cindy Whitehead told NPR. Trials of the drug have demonstrated some modest improvements in women who have HSDD. 

The drug must be taken daily. Side effects include nausea, dizziness and drowsiness. It's been rejected twice by the FDA, once in 2010 and again in 2013. The agency has said the potential risks outweigh its “modest” impact on sexual satisfaction.

But Susan Scanlan, chairwoman of Even the Score, said Viagra and some other drugs have more serious side effects, including blindness and penile rupture. “The implication is that men can be trusted to make a rational decision of risk versus reward and women can’t,” she said.

A spokeswoman for the FDA said the agency “strongly rejects claims of gender bias,” the New York Times reported.