Pre-exposure prophylaxis for HIV infection: how antiretroviral pharmacology helps to monitor and improve adherence

Pre-exposure prophylaxis (PrEP) with antiretroviral drugs is a novel biomedical intervention that can prevent HIV transmission among high-risk populations. As findings from multiple PrEP studies have suggested that adherence is vital to achieve the full prevention benefits of PrEP, it is important to understand the clinical pharmacology and pharmacokinetic (PK) properties of PrEP antiretrovirals, the association of PK and PrEP efficacy and the potential for drug concentration measurement to be used as a tool to monitor PrEP adherence. In this review, we examine studies related to PrEP adherence with attention to the clinical pharmacology and pharmacokinetics of current and novel PrEP agents. Studies of animal models, pharmacokinetics and clinical trials related to PrEP and adherence were reviewed. In summary, when combined as part of a comprehensive prevention strategy that includes use of condoms and risk reduction counseling, PrEP has tremendous promise as a adjunctive biomedical HIV prevention intervention, providing that adherence is maintained.