Intercourse-Based PrEP Dosing Lowers HIV Risk in Gays, But Why?

Original Article:

A strategy of taking Truvada (tenofovir/emtricitabine) as pre-exposure prophylaxis (PrEP) only in the days surrounding intercourse, instead of daily as is typical, reduced the overall risk of HIV by 86 percent among a group of men who have sex with men (MSM). However, the ongoing study has thus far failed to determine whether the dosing protocol itself was responsible for the reduction in risk, as opposed to the fact that the study participants ultimately wound up taking Truvada with some level of regularity.

Preliminary results from randomized, placebo-controlled IPERGAY trial were presented at the 20th International AIDS Conference in Melbourne, Australia, in July. Researchers presented these updated results at the 2015 Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle.

The study, which began in February 2012, included 414 HIV-negative MSM at six sites in France and one in Canada. The participants, who were at high risk for HIV because they did not use condoms consistently with their sexual partners, were randomly assigned to receive either Truvada or a placebo. They were instructed to take two doses of the drug between 24 and two hours before intercourse (or one pill, if the most recent dose was taken between one and six days before), and then, if intercourse did occur, to take one dose every 24 hours after that first dose, until they had taken two pills since the last time they had anal sex. This means that during a week in which someone had sex he would take a minimum of four pills, or a maximum of eight. 

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