Flibanserin Studies Continue: Will It Ever Become The Female Viagra? | HealthInfi

The libido enhancement drug flibanserin (trade name Addyi) took center stage last week after winning long-sought approval from the U.S. Food and Drug Administration (FDA). The coverage from advocates and nonbelievers has run the gamut—advice, caution, and criticism likely to confuse undecided—but curious—onlookers. But exactly how Addyi drums up sex drive is still murky.

The drug has a long backstory. It was originally investigated in 1995 by pharmacologist Franco Borsini and a team of researchers at Boehringer Ingelheim Italia in Milan as an antidepressant because of its ability to regulate neurotransmitters—the brain’s chemical-signaling molecules. In particular, the team suspected that the drug regulated three key neurotransmitters thought to influence mood: serotonin, dopamine, and norepinephrine.

A clinical trial found it did little to alleviate depression, but did seem to have an effect on mood. It just wasn’t the mood the researchers were expecting. These early trials tipped clinicians to flibanserin’s more prominent role in sexual health, as female subjects had higher scores on the Arizona Sexual Experience Scale, a survey that asks participants to rate their satisfaction on a variety of sexual health topics, like how often participants felt sexual desire and how intense that desire was.

A separate group of researchers, also at Boehringer Ingelheim, completed their first clinical trials to explore flibanserin as a libido-enhancer in 2008. They measured levels of desire through a journal-based evaluation in which subjects recorded their levels of sexual drive on a daily basis. But FDA twice concluded that the resulting increases in libido were not statistically significant, and regulators were wary of potentially dangerous side effects like dizziness, sleepiness, nausea, and fainting.

So what turned FDA’s red light green? For one: the parameters of the trials. Clinical investigator on the latest Addyi trials Sheryl Kingsberg explains that the evaluation of sexual desire in the brain is not a particularly clear-cut measurement. As the three clinical trials progressed over the course of about 8 years, so did techniques in determining desire, says Kingsberg, a reproductive biology and psychology researcher at University Hospitals Case Medical Center in Cleveland, Ohio, and consultant to Sprout Pharmaceuticals, which bought flibanserin from Boehringer Ingelheim in 2011, and was in turn purchased last week by Valeant Pharmaceuticals.Read More