Use of lubricants with anal sex associated with increased risk of rectal sexually transmitted infections

Published on May 27, 2010 at 8:55 AM · No Comments

New research presented at International Microbicides Conference

The risk of acquiring HIV through unprotected anal sex is at least 20 times greater than with unprotected vaginal sex and increases if other infections are already present in the rectal lining. Could the use of lubricants - at least certain kinds - be another risk factor among men and women who engage in receptive anal intercourse? Two studies presented today at the International Microbicides Conference in Pittsburgh, suggest the answer is yes.

In one study involving nearly 900 men and women in Baltimore and Los Angeles, the researchers found that those who used lubricants were three times more likely to have rectal sexually transmitted infections (STIs). Another study that subjected popular over-the-counter and mail-order lubricants to rigorous laboratory tests discovered that many of the products were toxic to cells and rectal tissue. If in humans, these products have the same effect, the cells might be rendered more vulnerable targets for HIV infection than they already are.

In the United States alone, receptive anal intercourse is practiced in up to 90 percent of gay and other men who have sex with men, according to International Rectal Microbicides Advocates. Moreover, the practice is not limited to men. U.S. estimates and surveys in the United Kingdom indicate between 10 to 35 percent of heterosexual women have engaged in anal sex at least once. Globally, estimates suggest 5 to 10 percent of sexually active women are having anal sex. While condoms are generally effective for protecting against HIV and other STIs, most acts of anal sex go unprotected.

Microbicides - substances applied topically on the inside of the rectum or vagina - could potentially help prevent the rectal transmission of HIV, and some are being tested in early Phase I safety studies. Another approach called oral pre-exposure prophylaxis (PrEP) involves the use of antiretroviral drugs to reduce the risk of HIV in HIV-negative people. A large Phase III trial of PrEP involving men who have sex with men in South America, Africa and the United States is expected to report results by early next year. Yet, if either of these approaches is found effective in clinical trials, they will do no good if those most at risk don't use them. Other research presented today sheds light on this issue. Summaries of all three studies are provided below.

M2010 is taking place May 22-25 at Pittsburgh's David L. Lawrence Convention Center. Nearly 1,000 participants from 47 different countries are attending the meeting to hear about the latest developments in HIV prevention research.

Use of lubricants with anal sex associated with more rectal STIs

Lubricants are typically used before and during receptive anal intercourse, but their use could increase the risk of rectal sexually transmitted infections (STIs), a study involving nearly 900 men and women in Baltimore and Los Angeles has found. Even after controlling for gender, HIV status, city, condom use, and number of sex partners in the past month, the association between lubricant use before receptive rectal intercourse and rectal STIs remained strong, reported Pamina Gorbach, Dr.PH, from the School of Public Health and the David Geffen School of Medicine at the University of California, Los Angeles, who led the study. According to the study's statistical analysis that considered the HIV status, gender, condom use and study site, participants who used lubricants before receptive anal intercourse were three times more likely to have a rectal STI. Although the analysis didn't consider the specific lubricants being used, it may be that certain types of products are more irritating to the lining of the rectum than others, which could increase men and women's vulnerability to rectal STIs, the researchers suggest.

The study, which was conducted between October 2006 and December 2008, examined the rectal health and behaviors of 879 men and women. Participants in the study were tested for gonorrhea and Chlamydia and asked about their sexual and hygiene practices in private computer-based interviews. Of the 879 participants, 421 reported having receptive anal intercourse in the past month (229 men) or in the past year (192 women) and of these 421, 302 provided the researchers with additional information about their use of lubricants. About half, or 147 (52.7 percent) said they used a lubricant when they last engaged in anal sex.

Of the 302 included in the analysis, 25 (8.3 percent) tested positive for a bacterial rectal STI (5.6 percent of women and 10.2 percent of men). But among those who said they recently used a lubricant, the number of STIs was higher. With STI test results available for 145 of the 147 recent users, the researchers found that 17 (11.7 percent) tested positive for a rectal STI compared to just seven (5.1 percent) of the 156 who said they did not use a lubricant. A higher percentage of African Americans (61.percent) reported using lubricants than did Hispanics (40.4 percent) and whites (23.2 percent). A higher percentage of HIV-positive participants (56 percent) were more likely to report using lubricants than were HIV-negative participants (43.7 percent). Most of the participants who reported using lubricants said they used a water-based lubricant (76 percent); 28 percent used silicon-based products, 17 percent oil-based lubricants and 6 percent said they had used numbing lubricants. More research will be needed to understand exactly how lubricants facilitate transmission of STIs, including HIV, the researchers say.

Study is first to evaluate safety of lubricants used in anal sex

A laboratory study that compared over-the-counter and mail-order lubricants commonly used with receptive anal intercourse found many of the products contain higher amounts of dissolved salts and sugars compared to what's normally found in a cell. As a result, the products had toxic effects on the cells and rectal tissue studied. Some of the lubricants caused significant portions of the epithelium - the layer of cells that serves as a protective barrier inside the rectum - to be stripped away. Conclusions cannot be made based on this study alone, though the results are compelling enough to wonder if these lubricants might have the same effect in people and thereby increase susceptibility to HIV, commented Charlene Dezzutti, Ph.D., from the University of Pittsburgh and Magee-Womens Research Institute, who led the study for the Microbicide Trials Network. The study, which was conducted in collaboration with International Rectal Microbicides Advocates (IRMA), was undertaken because little is known about the safety of lubricants even though they are frequently used during anal sex.

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