A daily pill known to prevent HIV transmission does not necessarily need to be taken every day, at least in some demographic groups, according to guidelines published by health officials in New York City and elsewhere who have found that the pill is still effective when dosages are based on when a person is planning to have sex.
Dubbed “PrEP on Demand,” men who have sex with men can take two pills between two and 24 hours before having sex and then another pill within 24 hours after having sex. One more pill must then be taken 24 hours later. If the individual continues having sex, he should continue taking PrEP daily until two days after the stretch of sexual activity ends.
A person who plans to have sex on a Friday night, for example, could take two pills on Friday afternoon, another pill on Saturday, and one final pill on Sunday — that is, if Friday is the only day that person has sex.
Around the time of WorldPride this past summer, the city sent doctors and other health professionals guidelines outlining the regimen as an alternative option for men who have sex with men, including those who cannot afford the cost of daily PrEP and those who have sex inconsistently, have kidney impairments, or would rather not take the pill every single day, according to the city’s Department of Health and Mental Hygiene.
“Part of that came from providers who were trying to do PrEP on Demand without really understanding what the dosage schedule was like,” said Dr. Demetre Daskalakis, the deputy health commissioner. “So it was an opportunity to alert people of an alternative strategy.”
Some people informally took PrEP on an on-demand basis even before guidelines were unveiled. That phenomenon was at the center of a 2018 study evaluating daily and non-daily dosing schedules for PrEP among 37 men who have sex with men in New York City. The study found participants “generally expressed preferences for non-daily dosing schedules, both because non-daily dosing corresponded to patterns of sexual activity and because they believed side effects of the PrEP medication would be less with less frequent dosing.”
But public health officials agree that intermittent doses can lead to adherence challenges in terms of both sticking to the 2-1-1 regimen and making sure to take it before sexual behavior occurs.
“Remembering regular non-daily doses was difficult on the time-driven schedule; in both time-driven and event-driven arms [of the study] forecasting sex in order to plan for dosing around sex was a challenge,” that study noted.
Importantly, the city’s health department still prefers that individuals take PrEP daily, and Daskalakis made it clear during a phone interview with Gay City News that PrEP on Demand is not being recommended. The guidelines have only been published in certain other locations, such as San Francisco. The Food and Drug Administration has approved only daily doses.
Studies evaluating the effectiveness of PrEP on Demand have been successful dating back several years. A 2014 trial of PrEP on Demand among HIV-negative men who have sex with men in France and Canada, called the IPERGAY study, showed such strong evidence in support of PrEP on Demand that the trial ended early.
Yet, while Daskalakis noted that PrEP for daily use is roughly 99 percent effective, he pointed out that the percentage of effectiveness for PrEP on Demand is somewhere “in the mid-80s.”
Even with reduced effectiveness, the on-demand regimen appears to be the next best option for individuals who refuse to adhere to a daily schedule. Daskalakis said he has patients who are at high risk for HIV “but they won’t take the pill every day.” He said he then explains in complete detail to his patients how to structure doses around sexual encounters, but that schedule proves to be far too complex for some of them.
“I’ll get a text or a call saying, ‘I don’t know how to do it,’” he explained. “Honestly, a pill a day is a lot more straightforward.”
Far more research is necessary to further understand PrEP on Demand among other demographics beyond men who have sex with men. Studies have not thoroughly examined PrEP on Demand’s impact among transgender individuals or cisgender women and it is not clear when the guidelines could expand beyond the existing demographics.
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