Concerns have been raised by the US Food and Drug Administration (FDA) about the safety of flibanserin, an experimental women's libido drug.

The drug has already been rejected by the FDA two times. The argument is that its benefit is not notable enough to outweigh its side-effects, which can include dizziness and nausea.

The agency said the drug increases the risk of fainting and accidental injury, especially when it's combined with alcohol.

On Tuesday, the review of the drug was published on the FDA's website. It came two days before a meeting of external advisers (advisory panels' advice is typically followed by FDA) will recommend whether it should be approved.

The privately-held Sprout Pharmaceuticals is seeking the approval of the drug for premenopausal women whose lack of sexual desire causes distress. If it gets approved, its proposed name will be Addyi.

The review conducted by The FDA showed a statistically significant improvement in the number of satisfying sexual events (SSEs) experienced by women taking the drug. It also showed a reduction in distress related to low desire. However, FDA's major concern is whether the drug's benefits outweigh the risks.

Dr. James Simon, an expert in female sexual dysfunction who was a clinical trial investigator for flibanserin, said, "My fear is that should this large protracted long-term development of flibanserin fail, the category of women's sexual health will lose research and development support".

After adjusting for an inevitable placebo effect from an average baseline of two to three SSEs a month, it was found that women had an increase of 0.5 to 1.0 SSEs a month.

They had a placebo-adjusted improvement of 0.3-0.4 on the distress score, and a 0.3 to 0.4 increase in desire based on a score known as female sexual function index (FSFI).