(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.