TUESDAY, Feb. 26 (HealthDay News) -- A vaginal microbicide gel that contains the antiretroviral drug tenofovir is safe for HIV-negative women to use every day, according to a six-month study of 200 women in India and the United States.

This study, by researchers at the U.S. National Institutes of Health-funded Microbicide Trials Network, looked at whether women were able to adhere to a regimen of either daily or sex-dependent use of the gel. Both regimens proved equally safe, and women's adherence to each regimen was similar. Notably, none of the women who used the new gel got HIV during the study period.

There were no differences in liver, blood and kidney function between women who used the gel and those who used a placebo, nor were there any differences in rates of genital symptoms such as itching and burning.

The compliance rate was 83 percent among women in the daily use group, and 80 percent among women instructed to use the gel within two hours of having sex.

The results are an advance in efforts to use microbicides to prevent HIV infection in women, the researchers said. Worldwide, almost half of people with HIV/AIDS are women, and 70 percent to 90 percent of all HIV infections in women are due to heterosexual intercourse. In many areas of the world, even married women and those with steady partners are at risk for HIV infection.

Correct and consistent use of male condoms prevents HIV infection, but it's often difficult for some women to convince men to use condoms.

"Finding that daily use is both safe and feasible is important, because we believe a daily approach may provide more sustainable protection against the virus in women who can't always predict when they will have sex," study leader Sharon L. Hillier, said in a prepared statement.

"Based on what we have learned, we can proceed with greater confidence on a path that will answer whether tenofovir gel and other gels with HIV-specific compounds will be able to prevent sexual transmission of HIV in women when other approaches have failed to do so. It is a critical time for all of us engaged in HIV prevention, and I truly believe we are turning a corner," said Hillier, director of reproductive sciences at the University of Pittsburgh School of Medicine.

Microbicides designed to prevent HIV infection are applied on the inside of the vagina or rectum.

The study was presented this week at Microbicides 2008, an international meeting in New Delhi, India.