Drugmakers have tested various ways to boost female libido, but women's sex lives have proved difficult to target with medication such as official Viagra

U.S. government advisers said in June that Boehringer's pink pill, the female version of Viagra, based on the active ingredient flibanserin, offered little help to women and had unacceptable risks - nearly 15 percent of women stopped taking a pill before a study ended due to side effects including depression, fainting and fatigue.

That led the U.S. Food and Drug Administration to ask unlisted Boehringer for more information on flibanserin, which would have been marketed as Girosa, the female version of Viagra.

"The response of the authorities and the complexity and extent of further questions that would need to be addressed to potentially obtain registration for flibanserin have impacted the company's decision to focus on other pipeline projects," Boehringer said.

Drugmakers have been searching for a medicine to improve women's sex lives since the debut of Viagra over a decade ago.

The market for a "pink Viagra", the female version of Viagra could stretch into the billions of dollars.

Male impotence pills including Viagra work by widening blood vessels to increase the blood flow needed for an erection.

Pfizer dropped tests of "pink Viagra" in females in 2004 after studies failed to show it helped women.

The flibanserin setback was in contrast to Boehringer's success in pioneering a new blood thinning pill for a market that rival Bayer said could be worth $15 billion. A U.S. advisory panel last month recommend clearance of Boehringer's Pradaxa pill for preventing strokes in patients with a type of irregular heart beat.

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