Pfizer Gives Up Testing Viagra on Women

By GARDINER HARRIS

Women, the maker of Viagra has found, are a lot more complicated than men.

After eight years of work and tests involving 3,000 women, Pfizer Inc. announced yesterday that it was abandoning its effort to prove that the impotence drug Viagra improves sexual function in women. The problem, Pfizer researchers found, is that men and women have a fundamentally different relationship between arousal and desire.

For men, arousal almost always leads to desire. So by improving a man's ability to have erections, Viagra measurably affects his sexual function. But arousal and desire are often disconnected in women, the researchers found, to their consternation.

Although Viagra can indeed create the outward signs of arousal in many women, that seems to have little effect on a woman's willingness, or desire, to have sex, the researchers said.

"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.

Pfizer's problem has been that its research effort has largely been led by cardiologists and urologists, said Dr. George Nurnberg, professor of psychiatry at the University of New Mexico School of Medicine. "Psychiatry hasn't been a major player," he said.

That is a mistake with women, he said, because psychology is more important in their sexuality than it is in men's.

Still, Viagra can be effective in some women, Dr. Nurnberg said. Women who once had normal sexual function but then suddenly lost all desire - often as a result of taking antidepressants - can be helped by Viagra, he said. Women who have always had low libido levels are unaffected by Viagra, he said.

"That's because hormones trump Viagra," said Dr. Jennifer R. Berman, assistant professor of urology at U.C.L.A. and director of the Female Sexual Medicine Center. Much of Pfizer's research found that the real factor in determining desire and sexual function in women is hormone levels, Dr. Berman said.

Procter & Gamble is testing a patch with testosterone, the male hormone, as a means of improving female sexual function. Some gynecologists are already prescribing testosterone for patients who complain of low libidos. Estrogen treatments and supplements are also commonly used.

The market for such treatments could be huge. A study published in 1999 in The Journal of the American Medical Association found that 43 percent of women experienced some form of sexual dysfunction, compared with 31 percent of men.

But that study has been roundly criticized, and some women's health researchers say the entire search for a female Viagra is wrong-headed. "The idea that there is some normal level of sexual functioning drives me up the creek," said Leonore Tiefer, a clinical psychologist in New York. "These companies believe that sex is matter of organ function, like breathing or excretion. I don't think there's an answer to the question of what women should want sexually."

But Dr. Boolel say critics like Dr. Tiefer are being insensitive. "To women who have it, female sexual dysfunction is real and distressing, and to say it's an invention is an insult to women's health," he said.

Karen Katen, president of Pfizer Global Pharmaceuticals, said the company's lack of success in its Viagra for women program was, unfortunately, all too typical. "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," she said.

Pfizer once had great hopes for its clinical program testing Viagra in women. Viagra works by blocking an enzyme that normally inhibits blood flow, causing penile tissue to swell. That enzyme is found in great quantities in the penis and is also found in the pelvic region of women.

In one early clinical trial, researchers gave six women Viagra and six others a placebo, sat them in front of erotic videos and used a pelvic probe to measure any change in genital blood flow. The sex organs of women given Viagra were more engorged than those given placebos. The program seemed to be succeeding, Dr. Tiefer said.

But a larger trial that included a questionnaire found that although Viagra was associated with greater pelvic blood flow, the women experiencing this effect did not feel any more aroused, Dr. Boolel said.

Pfizer researchers spent years trying to find some well-defined group of women for whom increased pelvic blood flow and desire could be linked. They failed, he said.

Dr. Marianne Legato, professor of clinical medicine at Columbia University and director of the Partnership for Gender Specific Medicine, said that the disconnection between arousal and desire in many women was so profound that they "often don't have any desire for sex until they are physically in the act of lovemaking."

Indeed, getting a woman to connect arousal and desire, Dr. Legato said, requires exquisite timing on a man's part and a fair amount of coaxing. "What we need to do is find a pill for engendering the perception of intimacy," she said.

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