Substance use interactive toxicity beliefs impede HIV pre-exposure prophylaxis use among men who have sex with men

Ending HIV epidemics hinges on antiretroviral therapies (ART), including their use in pre-exposure prophylaxis (PrEP). Unfortunately, PrEP use remains low among populations that could benefit most. PrEP use is impeded by multiple barriers including concerns about side-effects and erroneous beliefs about hazards of mixing PrEP with alcohol and other drugs. The current study tested the hypothesis that substance use interactive toxicity beliefs would mediate the association between concerns about PrEP side-effects and four separate PrEP use outcomes: past use, current use, uptake, and adherence. Black HIV negative men who have sex with men (n = 436) completed baseline and up to 18-months of follow-up for measures of demographic and health characteristics, PrEP use, concerns about PrEP side-effects, and substance use interactive toxicity beliefs. All participants reported alcohol or other drug use in the past two-months at baseline. Cross-sectional mediation analyses confirmed our hypothesis, showing that concerns about PrEP side-effects were directly associated with past and current PrEP use, and these associations were mediated by interactive toxicity beliefs. Prospective models did not confirm mediation but showed that greater substance use interactive toxicity beliefs significantly predicted PrEP uptake and adherence. These results support the importance of substance use interactive toxicity beliefs as a barrier to PrEP use and warrant interventions to address underlying biases and misinformation.