The HIV pre-exposure prophylaxis medication known as PrEP is currently recommended for the prevention of HIV acquisition in populations at higher risk such as gay and bisexual men (GBM). The number of eligible and recommended people taking PrEP, about 136,000 people as of mid-2017, is a significantly small percentage of the number at risk for HIV – about 1.2 million individuals. Although the rate of adoption of PrEP has been increasing over the last several years, with prescriptions having increased 73 percent each year since 2012, there remain concerns that those who are on PrEP may not adhere to the regimen well enough to benefit from its protection. Adherence to a daily PrEP regimen ensures its maximum protective effect, so it is critical to understand how GBM respond and possibly adjust their behavior in the event of missed PrEP doses. In a paper published in the journal AIDS Education and Prevention, CUNY Graduate School of Public Health and Health Policy Professor Christian Grov and colleagues examine how users respond when their PrEP regimen is interrupted.

Grov and a team of researchers conducted one-on-one qualitative interviews with 104 GBM in New York City who were on a daily PrEP regimen. Each participant was asked how they “made up” for missed doses, as well as their reflections on how having missed doses impacted their subsequent sexual behavior, if it did. Using thematic analysis, the researchers identified three distinct, but sometimes overlapping, behavioral responses to having missed a PrEP dose: 59 percent of participants reported continuing with their next dose as scheduled, 49 percent described ‘making up’ for a missed dose by taking the medication as soon as possible, within 24 hours of its scheduled dosing time, and 11 percent reported ‘doubling’ their next PrEP dose. When asked whether participants made adjustments to their sexual behavior in response to a missed dose of PrEP, participants provided varied narratives about their behavior after a PrEP regimen interruption. 54 percent reported making no changes to their sexual behavior, 49 percent described adjusting their sexual behavior to minimize risk, and 10 percent said the decision to adjust behavior would be contingent upon how many doses were missed. Many of the participants reported engaging in multiple behavioral responses.

The study found that, for the most part, participants took the PrEP medication in accordance to clinical guidelines. Even when missing a dose, their ‘make up’ methods paralleled recommended courses of action. Currently, CDC guidelines suggest that, in the event of a missed dose, patients should take their pill as soon as they remember—unless this would mean taking two pills within a few hours of each other, in which case patients are advised to wait until their next regularly scheduling dosing time. While participants’ beliefs on how to medically mitigate the effect of a missed dose were in line with current guidelines, participants varied in their reports of how best to navigate sexual behavioral response to minimize HIV risk in after a missed dose, particularly in reference to specific sex acts (e.g., oral versus anal sex). In terms of sexual behavior, Grov explains that participants understood that PrEP was “forgiving” of the occasional missed dose and thus some said they would not change their sexual behavior. For those that did change their sexual behavior, it was always in a way to reduce HIV risk (e.g., abstain from sex, engage in oral sex instead of anal sex, use a condom) but there wasn’t universal agreement on how “much” someone should change their sexual behavior.

The results of the study highlight that PrEP users make decisions about sexual behavior based on an assessment of their protection from PrEP. Though most participants understood that their protection from PrEP decreased with multiple missed doses, there was considerable variation in their beliefs about how much protection was retained for given sex acts. The paper points out that this ambiguity marks not only an important opportunity for healthcare providers serving GBM that are on a PrEP regimen to provide guidance, but also the need for clearer pharmacological data about how variations in PrEP blood concentrations protects against HIV across a variety of sex acts in the hours and days since a dosing lapse began.

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