The US Food and Drug Administration (FDA) has approved a libido-enhancing drug for women that has been dubbed "Female Viagra".

Flibanserin, a drug produced by Sprout Pharmaceuticals, recently passed an FDA advisory committee meeting.

The pill is designed to assist premenopausal women regain their sex drive by boosting levels of certain brain chemicals.

The drug has been criticised as having marginal effects.

Versions of the pill, which will be marketed as "Addyi", have been submitted for approval in the past but never passed.

It was rejected by the FDA twice for lack of effectiveness and side effects like nausea, dizziness and fainting.

Women taking the drug reported between half and one more sexually satisfying event per month - results experts admitted were "modest".

Originally the drug was produced by German company Boehringer Ingelheim. Sprout bought the drug from that company after it was turned down by the FDA.

Documents from the 4 June FDA advisory meeting describe the drug's purpose as "treatment of hypoactive sexual desire disorder (HSDD) in premenopausal women".

Women would take it each night.

A doctor would have to determine whether a woman seeking the pill was suffering from a disorder characterised by a lack of sexual fantasies and desire, causing the woman distress.

Currently, there is nothing on the US market approved for treatment of HSDD or another condition, female sexual interest/arousal disorder (FSIAD).

"This condition is clearly an area of unmet medical need," the FDA documents said.

Sprout only has 25 employees. Large pharmaceutical companies like Pfizer, Bayer and Proctor & Gamble have all studied female sexual desire disorder treatment but abandoned plans to pursue it.

Sprout's CEO, Cindy Whitehead, told AP they would promote Addyi carefully.

"We would never want a patient who's not going to see a benefit to take it and tell everyone it doesn't work," she said.

Lobbying by Sprout Pharmaceuticals was backed by the women's rights group. Even the Score, which has accused the FDA of gender bias by approving a number of drugs treating erectile dysfunction in men without passing an equivalent for women.