Clinical tests of the anti-impotency drug Viagra have failed to prove it helps women achieve sexual arousal.
Pharmaceutical giant Pfizer said it was "disappointed" the eight-year-long study showed Viagra is not useful in treating female sexual disorders.
It said it will not be seeking approval from drug regulators in the US to make the drug available to women.
Viagra is one of most popular drugs in the world for the treatment of erectile dysfunction among men.
Placebos
Pfizer said its scientists carried out tests on about 3,000 women since 1996.
"
This is the nature of drug development
"
Karen Katen, Pfizer Global Pharmaceuticals president
It said some of the women were issued with placebos and some with Viagra.
While the Viagra was found to be harmless, its degree of effectiveness could not be conclusively determined.
"While we were disappointed that the FSAD [female sexual arousal disorder] programme was not more successful, this is the nature of drug development," said Pfizer Global Pharmaceuticals president Karen Katen.
The company said it is studying other forms of treatment for FSAD.
Since Viagra was introduced in 1998,more than 23 million men have been prescribed the drug worldwide, Pfizer says.
Annual sales are worth nearly $2bn.
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