Women who lose their sexual appetite as a side effect of taking antidepressant could easily gain it back if using Pfizer Inc.’s Viagra, usually prescribed for impotency in men, new research in the July 22 issue of the Journal of the American Medical Association reveals.

According to background information of the study, about 70 percent of men and women taking antidepressants for major depression experience sexual dysfunction. Women generally experience painful intercourse, lose their desire, and end up without having orgasm while being prescribed antidepressants. These side effects bother both women and men so much that up to 70 percent stop taking their medication for depression within the first few months, co-author of the study Julia Heiman, director of the Kinsey Institute for Research in Sex, Gender, and Reproduction at Indiana University, said.

Why antidepressants slow sexual appetite? Previous research has shown that these drugs usually increase the chemical serotonin in the brain, which is thought to slow orgasm, most probably by diminishing the release of another brain chemical, dopamine.

For the study, conducted at seven US research centers between September 2003 and January 2007, the researchers divided 98 women taking antidepressants, average age 37 and all premenopausal in two groups: half of them were given Viagra and the other half were given a placebo for the eight-week study. None of the women knew which pill they were taking.

The woman involved in the study had been taking antidepressants (Celexa, Effexor, Paxil and Zoloft) for two years and has suffered sexual problems for at least four weeks. These antidepressants comprise up to 90 percent of the 180 million antidepressant prescriptions filled in the US each year.

After eight weeks, the researchers found that 73 percent of the women on placebo had no improvement in sexual functioning but only 27 percent of the women given Viagra reported no improvement. More exactly, the women taking Viagra reported an improved ability to reach orgasm and increased orgasm satisfaction. On the other hand, the study did not find significant differences in terms of desire or lubrication.

“What Viagra did was increase the orgasm and the time to orgasm. But it didn’t increase drive and desire,” said Harry A. Croft, MD, medical director of the San Antonio Psychiatric Research Center in Texas and a co-author on the study.

Previous research made by Dr. Nurnberg and colleagues reported in the Journal of Clinical Psychiatry showed that Viagra was helpful for men who suffered from erectile dysfunction because using antidepressant medications.

“By treating this bothersome treatment-associated adverse effect…patients can remain antidepressant-adherent, reduce the current high rates of premature medication discontinuation, and improve depression disease management outcomes,” Dr. H. George Nurnberg, MD, the study’s lead author and a professor at the University of New Mexico School of Medicine in Albuquerque and his colleagues wrote in the study.

“What Viagra does in women with normal testosterone [levels] is engorge their clitoris [with blood], which allows them to have orgasm. Viagra acts on a man's penis and a woman's clitoris,” Irwin Goldstein, MD, director of sexual medicine at Alvarado Hospital in San Diego and editor-in-chief of The Journal of Sexual Medicine told WebMD.

The study showed no serious adverse effects. Headaches were the most common side effects, being reported by 43 percent of the women on Viagra and only 27 percent of those on placebo. Also, 14 percent of the women on Viagra reported transient vision disturbances compared with 2 percent of those on placebo. Indigestion and reddening of skin were also reported more often by the women on Viagra.

The study was funded by Pfizer whose spokesperson, Sally Beatty said the company has no plans to pursue FDA approval for using Viagra as a treatment for female sexual dysfunction.

Viagra sales totaled $1.76 billion last year, up 6 percent from 2006, Pfizer reported in January. The drug was approved in 1998 and was the first impotence treatment available as a pill.