Taking an anti-HIV drug "as needed," rather than every day, can also dramatically reduce the odds of contracting the AIDS virus among high-risk people, according to a new study published Tuesday in the New England Journal of Medicine.
Those who took the antiretroviral drug, Truvada, just before and after sex, were 86 percent less likely to contract the disease than those who took a placebo, said the study, led by Jean-Michel Molina of Hopital Saint-Louis in Paris and Jean-Francois Delfraissy of France's ANRS Research Agency.
Previous studies have shown some efficacy of Truvada as a preventative medicine when taken every day, however adherence was a great challenge. In fact, low adherence is considered as one of the reasons why two recent trials involving heterosexual women failed to show any benefit of the drug.
Therefore, this "as-needed" strategy was designed to determine if high-risk people would gain benefit from it.
The researchers looked at 400 gay men and transgender women in France and Canada, who are at high-risk of HIV transmission, defined as persons having had unprotected anal sex with two or more different partners within a six month period.
Participants were instructed to take two pills before sex, a third pill 24 hours later, and a fourth pill 24 hours after that. When sexual intercourse happened more often, participants were told to take one pill per day and then the two post-exposure pills.
All study participants received regular HIV and sexually transmitted disease prevention counseling and services, and stocks of condoms and lubricant.
During a median follow-up of 9.3 months, participants in both groups took a median of 15 pills per month, demonstrating that they felt able to judge when the medication needed to be taken, Cecile Tremblay of the University of Montreal, who led the Canadian component of the research, said in a statement.
However, 28 percent of the participants did not take the pills at all and a further 29 percent took them at a suboptimal dose, Tremblay said.
In total, 14 of the 201 people in the placebo group acquired HIV, compared to two in the 199-strong Truvada group.
"Indeed, the two people in the medication group who became infected had not medicated themselves," Tremblay said. "This study clarifies the role Truvada can play in protecting this (high-risk) population."
The researchers pointed out that the efficacy of the long-term efficacy of strategy evaluated in their study needs to be further studied as it was relatively short and people's adherence to medication regimes tend to drop off over time.
