DoxyPEP stands for Doxycycline Post-Exposure Prophylaxis. Let’s break that down: Doxycycline is a type of antibiotic that is used to treat multiple types of bacterial infections (including STDs and STIs). “Post-exposure” refers to the period of time after the possibility of exposure to an STD (such as after a sexual encounter where condoms weren’t used). “Prophylaxis” is an action taken to prevent disease. If you’ve engaged in sexual activity and are concerned about your STI risk, you can take DoxyPEP within 72 hours to prevent common bacterial STIs from taking hold in your system.