Safety concerns over female libido drug Addyi

The only female libido drug approved by the FDA appears to cause a host of side effects, while only marginally improving sexual satisfaction in those taking it, according to a new review published in JAMA Internal Medicine.

Flibanserin, sold under the brand name Addyi, was approved last summer and was touted as a victory for women suffering from low sexual desire.

But the new research found that the drug's benefits are minimal.

"What we found was that women had on average 2.5 satisfying sexually events per month before entering the study and flibanserin added one half additional satisfying sexual events per month," said senior study author Ellen T.M. Laan, Ph.D., professor of sexology and psychosomatic gynecology at the University of Amsterdam, in the Netherlands.

What's more, the drug was associated with a number of side effects, quadrupling the risk of dizziness and sleepiness and more than doubling the chance of nausea. The drug also increased the risk of fatigue by more than half.

For the study, the researchers reviewed eight clinical trials -- five published and three unpublished -- that included almost 6,000 women.

The controversy around flibanserin is nothing new. The drug had been rejected twice by the FDA before receiving approval, and still faced criticism when it was cleared to market last summer.

"The FDA's own internal reviewers had recommended for rejection," Dr. Tara Narula told "CBS This Morning." "The concern is that it has limited efficacy or benefit ... significant side effects, and possibly a lack of science to elucidate the bigger picture when this drug goes into the real world," including possible interactions with other medications or health conditions.

Narula pointed out that demand for the drug did not really live up to what was expected, which might be partly attributed to the potential risks. Only 227 prescriptions for flibanserin were filled in its first few weeks on the market, Bloomberg reported.

It's also difficult, Narula said, to know how much influence advocacy groups like Even the Score -- which campaigned "to level the playing field when it comes to the treatment of women's sexual dysfunction" -- had in the FDA's decision to approve the drug.

"I think it's going to be really hard to tease out if there was political pressure or if the advocacy campaign Even the Score, that was very strong around the time of the approval, had anything to do with the FDA's decision," she said.

The drug was rejected in 2009 and in 2013. Two years later, when the drug was finally approved, there was not much additional scientific data available on its risks and benefits.

"The question really remains how much that PR and advocacy push to the media, to the FDA and to Congress had on this decision," Narula said.

Valeant Pharmaceuticals, which bought Addyi from Sprout Pharmaceuticals for $1 billion, said in a statement that it disagreed with the methodology used in the JAMA review.

"It is crucial that women suffering from HSDD are able to speak to their physicians about the full range of options -- including medical treatment -- to manage this serious and well-established condition," said Valeant Chief Medical Officer Dr. Tage Ramakrishna.

In an accompanying editorial in JAMA Internal Medicine, Dr. Steven Woloshin and Dr. Lisa M. Schwartz argued that the FDA's decision to approve the drug came too soon.

"The flibanserin saga is unsatisfying. The FDA approved a marginally effective drug for a non-life-threatening condition in the face of substantial -- and unnecessary -- uncertainty about its dangers," they wrote. "Women with distressing sexual desire problems need good treatments. We all need a drug approval process that delivers good decisions based on adequate evidence."