It's a common side effect of many antidepressants: decreased sexual function. For years, doctors have known that men with the problem can get help from Viagra. Now a study confirms that the little blue pill may also help women.
The research, which appears in today's Journal of the American Medical Association, found that women who took Viagra reported increased levels of sexual functioning, compared with those who took a placebo.
"It worked well for this group, not quite as strong as the men, but better than any other medicine [for sexual dysfunction]," said Dr. Paula Hensley, a University of New Mexico psychiatrist who is one of the study's investigators.
The study was funded by Pfizer Inc., the drug company that makes Viagra. Pfizer says it has no plans to market the drug to women.
Sexual medicine experts said the results were intriguing, but not groundbreaking, since some specialists already use Viagra for some female patients with sexual problems.
"This is empowering women who have sexual problems," said Dr. Irwin Goldstein, director of sexual medicine at Alvarado Hospital in San Diego.
Goldstein said he already uses Viagra with many of his female patients, but agreed that it doesn't work for all women.
Others were less impressed. "It's not a blockbuster study, but it's interesting," said Leonard Derogatis, director of the Center for Sexual Medicine at Sheppard Pratt Hospital in Towson. "The large majority of women with sexual dysfunction do not respond to Viagra."
Sexual problems are widespread - about 40 percent of women and a third of men report problems. Researchers and drug companies have developed a variety of treatments, but there are no drugs specifically approved by the Food and Drug Administration to help women with sexual problems. Goldstein said that any attention to the issue of female sexual dysfunction is welcome.
But many researchers questioned how useful Viagra would be for women. Most women with sexual problems suffer from a lack of desire, while men with sexual problems are more likely to suffer from lack of arousal, the physiological ability to become excited. In men, Viagra works on arousal by increasing blood flow to the penis.
"Viagra is not a desire drug. It dilates the blood vessels, allowing intercourse to occur," said Rutgers University psychology professor Barry R. Komisaruk, an expert on sexual dysfunction.
Shepard Pratt's Derogatis agreed: "The most prevalent female sexual dysfunction is not arousal but desire. Viagra doesn't have a direct effect on that," he said.
Some women who have tried Viagra say their experience fits this view. "It doesn't work for desire," said Lillian Arleque, an executive coach and writer who lives in Andover, Mass. She began taking Viagra several years ago. "When you take Viagra it increases blood flow to your genitals. It increases sensation."
Arleque, 62, collaborated with Goldstein's wife, Sue, on When Sex Isn't Good, a book on female sexual dysfunction.
Hensley, the study investigator, said the key is targeting the right patients. "You need a woman who had good sexual function before taking antidepressants, and whose sexual problems were clearly a function of the [drugs]," she said.
For men, Viagra has been extremely successful. Since being introduced 10 years ago, it has been used by 35 million men around the world, according to Pfizer, which sold $1.76 billion worth of the drug last year.
"It's a drug that has changed society, and the world," said Goldstein.
After Viagra was introduced, Pfizer tested it extensively in women. Although it was safe, it wasn't particularly effective, and Pfizer stopped studying it in 2004.
A spokeswoman said the company is not currently pursuing FDA approval of Viagra for female sexual problems, a process that involves years of extremely expensive trials. "Pfizer currently has no plans to pursue an indication for Viagra as a treatment for female sexual dysfunction," said Sally Beatty, a Pfizer spokeswoman.
Although the company funded the research published today, it did not initiate the study, but instead awarded a grant to the researchers.
The study grew out of earlier work by the same researchers. A decade ago, New Mexico psychiatrist Dr. George Nurnberg and colleagues examined whether Viagra worked on men who were taking antidepressants. When the study found that Viagra helped, the researchers moved on to women who were taking the same antidepressants.
The drugs, known as selective serotonin reuptake inhibitors, or SSRIs, are consumed by millions of people with depression. Doctors write more than 160 million SSRI prescriptions a year, mostly for women, who suffer from depression twice as often as men.
SSRIs increase brain levels of a key neurotransmitter, serotonin. But increased serotonin often causes sexual problems in both sexes.
"It is the ultimate inhibitor of sexual function," Goldstein said, noting that a third of women who come to him with sexual problems are taking SSRIs.
The study examined 98 volunteers, all taking the antidepressants, who were evenly divided into two groups. One group received Viagra, the other a placebo. The researchers found that only a quarter of the women taking the placebo reported improvement with treatment, compared with 72 percent of women taking Viagra.
Hensley said she has tried Viagra on a few of her female patients. "I think it's worth a try. It's a pretty benign drug. It's either going to work or it's not," she said.
But the drug is not approved by the FDA for use in women, and insurance companies often don't cover it. So Hensley prescribes it less because it costs patients so much.
Several companies are now working on drugs that target female sexual problems, particularly decreased sexual desire. Both Derogatis and Goldstein said they expect some to win FDA approval.
"In five years," Derogatis said, "you will have several female drugs on the market."