Vulnerable Periods: Characterizing Patterns of Sexual Risk and Substance Use During Lapses in Adherence to HIV Pre-exposure Prophylaxis Among Men Who Have Sex With Men.

Abstract

Pre-exposure prophylaxis (PrEP) is highly efficacious, but some groups of men who have sex with men may have difficulty adhering to daily dosing. Prevention-effective adherence suggests that PrEP's efficacy depends on adherence at the time of HIV exposure; yet, few studies have examined how exposures (ie, high-risk sex) overlap with periods of consecutive missed PrEP doses. Substance use may also play a role in these vulnerable periods. We used digital pill bottles to monitor the daily adherence of 40 PrEP-experienced patients recruited from an outpatient clinic in the Northeastern US over a six-month period. Participants also completed detailed online diaries every 2 weeks during this time that surveyed their sexual behavior and substance use each day. Daily adherence was high overall (M = 83.9%, SD = 18.0%), but 53% (N = 21) had a lapse of > 3 consecutive daily PrEP doses over 6 months. Participants' rate of engaging in high-risk condomless anal sex (CAS) did not differ across lapse days versus continuously adherent days. Alcohol use was not associated with engaging in CAS during a PrEP lapse. However, participants reported engaging in CAS significantly more often during a PrEP adherence lapse on days when they also used stimulant drugs. Men who have sex with men may have periodic difficulty adhering to PrEP at the specific times when they are at risk. Stimulant drug use could play an important role in increasing HIV risk specifically during adherence lapses.