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Study Shows PrEP Works Effectively “On Demand”

Study Shows PrEP Works Effectively “On Demand”


Taking Truvada at least 2 hours before sex and several days after can prevent HIV--but not as well as the daily pill. 

Pre-exposure prophylaxis has been shown time and time again to be effective in combating HIV infection, although long-term adherence to the regimen can be challenging. That’s why researchers have been looking at options to the one-a-day pill.

Jean-Michel Molina of the University of Paris Dederot evaluated the possibility of an “on demand” regimen using results from the IPERGAY study. The results, announced at CROI  demonstrate that taking two pills between two to 24 hours before sex and one additional pill each of the following two days, does prevent HIV transmission. With an HIV incidence reduction of 86 percent in those taking it as described, this method of taking PrEP isn’t perfect but presents a very viable alternative for long-term daily adherence.

The IPERGAY study was halted back in 2014 due to high efficacy of the on-demand regimen and in order to get PrEP to all 400 men, not just those in the experimental group. This early evidence of efficacy was shown to hold true based on Molina’s findings.

Regardless, the Center for Disease Control and Prevention recommends that PrEP be taken at least seven days before a possible exposure while urging PrEP users to stick to daily regimens. “While two pills the day before sex is better than none,” explained Dr. Robert Grant, medical director for the San Francisco AIDS Foundation, “the highest level of protection comes after five to seven daily doses for rectally exposed men (and 20 daily doses for women)…Two tablets before infrequent sex probably does not provide the same high level of protection that we see with daily dosing.” 

At this point, PrEP on demand has not benn approved by the  FDA and therefore cannot be prescribed by doctors. Still, this study verifies the voracity of the on demand option.

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