Assessing the Efficacy of Prolonged Doxycycline PEP Use in High-Risk Populations for STI Prevention

First recommended in October 2022, doxycycline post-exposure prophylaxis (DoxyPEP) has been increasingly used as a treatment for multiple sexually transmitted infections (STIs). To evaluate the efficacy of prolonged DoxyPEP use in high risk populations - men who have sex with men (MSM) and transgender women - for STIs, different sources addressing various aspects of DoxyPEP, its efficacy in STI prevention, and the potential consequences of its widespread use in terms of antimicrobial resistance were examined. Across 9 studies, DoxyPEP was found to decrease the incidence of bacterial STIs, specifically, syphilis, chlamydia, and gonorrhea with varying efficacy, especially for gonorrhea. Furthermore, because there was no consensus on impact on resistance, the differential impact of DoxyPEP across STIs may be influenced by factors such as bacterial susceptibility to doxycycline, optimal drug concentrations to achieve desired effects, and emerging resistance patterns essential in optimizing DoxyPEP usage.