Abstract
INTRODUCTION: Stimulant and heavy alcohol use are prevalent and associated with elevated risk for HIV seroconversion among men who have sex with men (MSM) and transgender women. In addition, each can pose difficulties for antiretroviral adherence among people living with HIV. Scant research has examined the associations of stimulant and heavy alcohol use with adherence to daily oral pre-exposure prophylaxis (PrEP) among MSM and transgender women. To address this gap in the literature, we evaluated the hypothesis that stimulant use and binge drinking are prospectively associated with sub-optimal PrEP adherence. METHODS: We analysed data from participants in a nested case-cohort in the iPrEx open label extension. Stimulant use (i.e. powder cocaine, crack-cocaine, cocaine paste, methamphetamine, cathinone) and binge drinking (i.e. ≥5 drinks in a single day) in the last 30 days were assessed. Baseline urine was tested for stimulants using immunoassays to reduce misclassification. Sub-optimal adherence was defined as tenofovir drug concentrations in dried blood spots less than 700 fmol per punch, indicative of less than four doses per week. We tested the prospective association of stimulant use and binge drinking with sub-optimal adherence at the 4-week follow-up visit. RESULTS AND DISCUSSION: Data from 330 participants were analysed. The majority of the participants were MSM (89%) with a median age at baseline of 29 years (interquartile range 24 to 39). Approximately 16% (52/330) used stimulants and 22% (72/330) reported binge drinking in the last 30 days. Stimulant users had fivefold greater odds of sub-optimal PrEP adherence compared to non-users in adjusted analysis (adjusted odds ratio [aOR] 5.04; [95% CI 1.35 to 18.78]). Self-reported binge drinking was not significantly associated with sub-optimal adherence after adjusting for stimulant use and baseline confounders (aOR 1.16 [0.49 to 2.73]). Depressive symptoms, being transgender, and number of sex partners were also not significantly associated with sub-optimal PrEP adherence (p > 0.05). CONCLUSIONS: Stimulant use is a risk factor for sub-optimal PrEP adherence in the month following PrEP initiation. Comprehensive prevention approaches that reduce stimulant use may optimize PrEP adherence. Creating adherence plans that specifically address PrEP dosing in the context of ongoing stimulant use should also be considered.