Prescribing Truvada (emtricitabine/tenofovir) to HIV-negative people as pre-exposure prophylaxis (PrEP) enjoys widespread support from infectious disease doctors—in theory, but not in practice. A large survey of physicians' attitudes in the United States and Canada found that three-quarters of those surveyed gave the thumbs-up to this HIV prevention tool, with just 12 percent unsupportive. And yet a scant 9 percent reported ever prescribing Truvada as PrEP to their patients.

Among the reasons for doctors' wariness were concerns about the possibility of what's known as “risk compensation”: taking PrEP and then engaging in riskier sex. However, a new study has echoed past findings that PrEP does not actually lead to this phenomenon.

Researchers at the Gladstone Institutes, an affiliate of the University of California, San Francisco, analyzed the reported sexual behavior of those in a large study of PrEP who believed both that they were taking Truvada, as opposed to the study's placebo, and that the drug was working. In theory, this group would be more inclined toward risk compensation, but this was not the case.

Robert M. Grant, MD, MPH, a senior investigator at Gladstone who led the study, says that the individuals he has researched over the years do not appear to want to change their sexual behavior because of PrEP.

“Many people tell me, ‘Look, I want raw sex, I'm going to get raw sex, the only question is whether I'm going to get HIV too,'” he says.