PrEP Adherence Not Decreased by Substance Use in MSM


A study found that while MSM who have used stimulant or non-stimulant substances had increased rates of STIs, PrEP adherence was not decreased by substance use.

In a new study of men who have sex with men (MSM) who were not infected with HIV, investigators found that although substance users had increased rates of sexually transmitted infections (STIs), pre-exposure prophylaxis (PrEP) adherence was not decreased by substance use.

A team of investigators from Austria, Colorado, and several southern California-based institutions assessed baseline and ongoing substance use over a 48-week period for stimulants and nonstimulant substances in a cohort of 394 participants (391 MSM and 3 transgender women) to investigate the association between substance use and adherence to PrEP, diagnosis of an STI, and completion of the study.

It has been previously thought that HIV-uninfected MSM and transgender women who have used stimulant or non-stimulant substances represent ideal candidates for PREP; however, the investigators hypothesized that substance users (in their study population) would have lower levels of PrEP adherence.

All participants in the study, published in the US Centers for Disease Control and Prevention’s (CDC’s) Journal of Emerging Infectious Diseases, were also enrolled in CCTG 595, a randomized controlled trial evaluating individualized text messaging versus standard care for adherence to daily PrEP.

At baseline and weeks 4, 12, 36, and 48, participants answered a substance use questionnaire that consisted of self-reported categorization of substance use activities in the previous 3 months including no use, some use, and frequent use, and identified whether the used substance was a stimulant or nonstimulant.

Substance use of any kind was reported by 288 (78%) of the participants and alcohol use of any kind was reported by 327 (83%) participants. Overall, substance use remained relatively stable over the course of the study, with 39% of participants reporting frequent substance use at baseline, and 42% reporting it at week 48.

The investigators determined adherence to PrEP by measuring intracellular tenofovir-diphosphate (TFV-DP) levels in dried blood spots (DBS). They noted that overall, 89% of participants at week 12 and 83% of participants at week 48 had adequate DBS TFV-DP levels (>719 fmoL/punch); 48% of participants at week 12 and 44% of participants at week 48 had estimated near-perfect DBS-TFV-DP levels (>1246 mmoL/punch).

A total of 322 participants (82%) completed the study at 48 weeks. From the total population of the initial 394 study participants, 279 reached the primary DBS adherence composite of adequate adherence and 115 participants reached the secondary DBS adherence composite of near-perfect adherence.

According to univariate analyses, there were no significant differences in the primary or secondary DBS adherence outcomes between individuals with or without ongoing substance or alcohol use (all P values >.2).

Overall, 152 of 394 participants (39%) were diagnosed with an STI during the study. STIs occurred more frequently in participants with ‘some’ and ‘frequent’ stimulation use at baseline.

In an explorative analysis, the investigators focused on the 39 individuals who left the study prior to the week 24 visit. They found that those individuals with baseline methamphetamine use had a greater tendency to leave the study early, but frequent baseline substance use tended to be associated with a lower tendency to leave the study early.

A limitation of the study is that DBS TFV-DP levels were only measured at 2 time points and that composite adherence did not account for missing follow-up data and time effects.

Notable takeaways from this study include that substance use was not associated with decreased adherence to PrEP, baseline frequent substance use was associated with higher likelihood of study completion, and baseline stimulant use was strongly associated with higher rates of incident STIs, suggesting greater sexual risk behavior in users of stimulant substances.

“Taken together, these findings indicate that substance use should not be used as a reason to withhold PrEP because of concerns about adherence,” the authors concluded.

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