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Ask the Doc: Is 'On Demand' PrEP Effective?

by Howard L. Scheiner, MD/AAHIVS
Wednesday Apr 22, 2015

Getting that beach-ready bod can mean more than lifts and crunches. In this week's Ask the Doc column, Dr. Howard Scheiner takes a realistic look at the latest studies around Pre-Exposure Prophylaxis (PrEP) with Truvada, and lets you know what you'll have to do to keep safe this summer.

If you're having high-risk sex or plan on doing so, Truvada appears even more effective than previously reported. But taking it "on-demand" a not yet approved indication is not without some unanswered questions and possible risk. If you're not having high risk sex, perhaps there are other methods of protection that would better suit your safer sex needs.

Just Ask the Doc, and you'll be sure to know what our expert thinks about issues around your HIV health.


Before You Go To Fire Island

Q: Dear Doc, I just went out to Fire Island for my first weekend. Everyone in my house is taking Truvada, except me so far. One of my housemates offered me one. I remember you had some advice a while back on Truvada being offered on the dance floor to prevent HIV when hooking up. So, what's the latest?

A: Truvada is a prescribed drug and shouldn't be taken from dance floor buddies. In the case of "on-demand" Truvada usage, one pill won't do the trick. You'll need two and another two "to go", but wait at least two hours before sex. This method may have to be repeated three to four times per week to maintain levels of Truvada in your body or it may not be effective.

While agreeably this answer is provocative, and I am far from advocating this approach, as daily PrEP remains the only approved treatment of choice for high risk sex, there is data supporting the "on-demand" dosing.

It is important to note that If you're currently on or looking to change your Truvada regimen, consult with your physician for the proper dosage and pill-taking protocol or the method of use may not prevent infection.

The IPERGAY study from France, recently reported results of the "on demand" prevention utilizing two Truvada before (2-24 hours before sex, one pill daily for the next two days). About 400 high-risk men who have sex with men (MSM) were randomized into two groups. One group received Truvada just prior to sexual intercourse and the other group a placebo. The results showed a significant difference in incidence between the two groups, with a significant reduction in the "on demand" PrEP group. The percentage reduction reported was 86 percent.

It seems that men in this study were taking PrEP three to four days/week on average (since the number of days they took it related to the frequency of sex).

While the FDA approved daily dosing of Truvada was approved in July 2012 as Pre-Exposure Prophylaxis (PrEP) to prevent HIV transmission, it now seems that possibly four doses a week may also be effective. Not only is the Ipergay study suggestive in this regard, but this is also based on data relating HIV incidence to the concentration of drug in the blood.

While it might appear that missing up to three doses in a week from the approved daily recommended dose is still effective, conversely, it is possible that men who have less frequent sex (once weekly) may not have the same benefit of "on demand" PrEP without the build-up of the drug to optimal levels from prior use.

Of note another study called PROUD, which looked at immediate versus deferred PrEP also showed an 86 percent reduction. This study used a "real world setting" of HIV-negative high-risk MSM who reported having bareback sex in the three months prior to enrollment. But, in this real world, PrEP was incorporated into existing risk reduction strategies, including condom use. The results translate to 3 vs. 13 new cases, out of 545 participants.

IPERGAY had 2 vs. 14 new cases out of 400 participants. Clearly, there is powerful and substantial efficacy, now showing an 86 percent reduction, which are the best numbers reported so far. Even so, some small number of men will convert despite PrEP.

Daily PrEP is still the only recommended way to go if PrEP is in your tool bag with some dosing forgiveness in that four days a week of dosing may still offer the significant protection demonstrated in the IPERGAY study.

"On Demand" PrEP is not yet ready for prime time.


Vulnerable to STDs While on PrEP?

Q: Am I more likely to get other STDs if taking PrEP. Why, and what should I believe?

A: Based upon the results from the PROUD study, which did incorporate condom use into PrEP strategies, the answer was no. There was no difference in the number of men diagnosed with other STDs between those on PrEP and those not on PrEP. Condoms are still the most effective way to prevent STD transmission.

Of course, whether the results of these studies from England and France translate to the "Real-World Setting" of New York City or Fire Island remains to be seen.


Called "more than a doctor, a trusted friend" by his patients, Dr. Howard Scheiner is a true native New Yorker. He was born in the Bronx, he attended the esteemed Bronx High School of Science and City University of New York before receiving his medical education at The Mount Sinai School of Medicine. Truly a Renaissance man, in addition to his lifelong service to the medical profession, Dr. Scheiner is a published author, playwright and musical composer. Combining all his loves, he is perhaps most proud of founding "The Brent Varner Project, Inc." a charity that provides free HIV services to those in need through the Actors Fund of America.


Ask the Doc

This story is part of our special report titled "Ask the Doc." Want to read more? Here's the full list.


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