Taking Truvada (tenofovir) as a pre-exposure prophylaxis (PrEP) to prevent HIV infection does not appear to increase overall sexual risk-taking among HIV-negative gay men, according to a study reported by aidsmap. The findings are clouded, however, by the fact that the participants received thorough HIV prevention counseling and services that may have counteracted inclinations to take greater sexual risks while relying on the apparent safety net of the drug.

A 2010 trial involving men who have sex with men found that Truvada lowered the risk of HIV infection by 44 percent on average, and that those with the greatest adherence—Truvada is supposed to be taken each day—saw a much better protective benefit.

Publishing their findings in the Journal of Acquired Immune Deficiency Syndromes, researchers studied 400 gay men for a 24-month period between 2005 and 2007 in this double-blind, placebo-controlled study.  

Participants were randomized into two groups, one that began Truvada immediately and another that did so nine months later. Researchers interviewed them at the outset and every three months thereafter about their sexual risk-taking and their use of recreational drugs and erectile dysfunction medications.  

At the beginning of the study, the group reported an average of 7.25 partners in the previous three months, a figure that dropped to 6 partners between months 3 and 9 and to 5.71 during the second year.  

Fifty-seven percent of the men reported unprotected anal intercourse during the three months before the study's baseline, a proportion that dropped to 48 percent between months 3 and 9 and then rose to 52 percent in the second year.

At the baseline, 29 percent of men reported unprotected intercourse with another man they knew to be HIV positive. This figure dropped to 21 percent between months 3 and 9 and to 22 percent during the second year.

Men did not report a significant change in the number of reported episodes of anal sex overall.

Episodes of unprotected sex with partners known to be HIV positive dropped from 2 at the outset to 1.37 during the second year. Meanwhile, unprotected anal intercourse with partners believed to be HIV negative increased from 2.75 at baseline to 4 during year two, suggesting that men were “serosorting,” which is when individuals attempt to mitigate the risk of HIV transmission by favoring sex with those they believe share their HIV status.

It is entirely possible that the study's findings are not representative of a real-world example of PrEP's effect on gay men's behavior, however. As the authors acknowledge, all the men in this study received risk-reduction counseling, condoms and lubricant, routine testing for HIV and sexually transmitted infections, and linkage to other prevention services, which the investigators write, “may explain the observed risk reduction and could explain the observed risk declines and could mitigate any potential for risk compensation.”

To read the aidsmap story, click here.

To read the study abstract, click here.