• Bloomberg


The safety of an experimental pill to treat low sexual desire in women, potentially the first of its kind in the U.S., is under scrutiny as regulators raised concerns the drug can act as a sedative and cause fainting.

The question of whether the modest benefit of the drug, flibanserin, is enough to outweigh serious side effects will be the topic of a meeting of advisers to the Food and Drug Administration on Thursday. The agency rejected the pill a year and a half ago, asking closely held Sprout Pharmaceuticals Inc. to perform more trials.

Since Pfizer Inc.’s iconic blue pill Viagra was approved by the FDA in 1998, sex drugs for men have become commonplace in the bedroom and the medicine cabinet. They’ve also been blockbusters — Viagra and Eli Lilly & Co.’s Cialis had sales of $3.98 billion last year.

There’s been nothing for women, however. Flibanserin would be the first drug approved to treat low female sexual interest and arousal.

FDA staff released a report Tuesday ahead of the advisory panel outlining effectiveness and safety concerns with flibanserin. The drug reviewers said that alcohol and other medications, including fluconazole for yeast infections, can increase the risk of passing out and sleepiness.

In clinical trials, the efficacy of flibanserin plateaued at eight to 16 weeks, though the risk of sleepiness and sedation, which occurred in almost 21 percent of patients on 100 mg of the drug, was highest the first month after beginning treatment, FDA staff wrote.

While some women may try hormone treatments like estrogen to treat low sexual desire, flibanserin works differently, acting on neurotransmitters that communicate information throughout the brain and body and can affect mood. The drug lowers the level of serotonin in the brain and boosts the amounts of dopamine and norepinephrine.

In a 2013 study published in the Journal of Sexual Medicine, women taking flibanserin said they had an average increase of 2.5 satisfying sexual events over a 28-day period, compared with 1.5 for those who took a placebo.

Sprout said the pill would be indicated for what’s called female hypoactive sexual desire disorder, defined as low libido that causes stress, in women who haven’t yet gone through menopause.

After it rejected the drug in 2013, the FDA asked Sprout to study whether sleepiness associated with flibanserin affected the ability to drive the next day. The trial found flibanserin “had no negative effect” on next-day driving, FDA staff wrote.

Sprout acquired the rights for flibanserin for an undisclosed amount from Boehringer Ingelheim GmbH in 2011, after the FDA told Boehringer that the drug hadn’t been proven safe or effective. Sprout conducted new tests with new measures of how women’s sexual desire was measured.

It’s not alone in seeking a treatment. Palatin Technologies Inc. is studying the drug bremelanotide for female sexual dysfunction. Palatin began enrolling patients in a final-phase clinical trial in December, according to the company’s website.