NEW YORK, Feb 28, 2004 (AP Online via COMTEX) -- Pfizer Inc. is ending research on whether the anti-impotency drug Viagra can be used treat female sexual problems because studies on women were inconclusive, the company said.

The results of several clinical studies involving about 3,000 women did not support a regulatory filing, Pfizer said Friday.

Karen Katen, executive vice president of Pfizer and president of Pfizer Global Pharmaceuticals, said that while the company was disappointed that the program was not more successful, "this is the nature of drug development."

"We make substantial financial investments, marshal the talents of our best scientists and clinicians, and spend years studying potential treatments only to find that they do not meet the requirements for regulatory approval," Katen said.

Experts agree that female sexuality is more complex than male sexuality, involving psychological and physical factors.

Joe Feczko, president of Worldwide Developing at Pfizer, said diagnosing sexual difficulties in women "involves assessing physical, emotional and relationship factors, and these complex and interdependent factors make measuring a medicine's effect very difficult."

At least 10 pharmaceutical companies have sought to develop a female equivalent for Viagra since the drug was launched in 1998 as a treatment for male sexual disfunction. More than 23 million men have been prescribed Viagra since then, Pfizer said.

Pfizer said it began researching into whether Viagra would work for women in 1996 and is studying other treatment approaches.
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There's a disconnect in many women between genital changes and mental changes," said Mitra Boolel, leader of Pfizer's sex research team. "This disconnect does not exist in men. Men consistently get erections in the presence of naked women and want to have sex. With women, things depend on a myriad of factors."

Dr. Boolel said that he and his team were continuing their research. But he said the researchers were changing their focus from a woman's genitals to her head. The brain is the crucial sexual organ in women, he said.

Drugs that affect brain chemistry "could be an extremely interesting area of investigation," he said.