Randomized Directly Observed Therapy Study to Interpret Clinical Trials of Doxy-PEP

Inclusion criteria

• not currently at risk of a sexually transmitted infection and willing to use other methods, such as condoms, for STI prevention;
• if diagnosed with an STI in the past two years and/or a partner was diagnosed with an STI in the past year, is willing to use condoms for STI prevention;
• willing to provide hair, blood, and urine samples;
• not currently enrolled in other STI prevention studies;
• able to speak English
• transgender women participants should be currently using estrogen gender affirming hormone therapy with blood estrogen levels demonstrating consistent use
• transgender men participants should be currently using testosterone gender affirming hormone therapy with blood testosterone levels demonstrating consistent use
• able to provide a hair sample of ~50-100 strands of hair that are non-gray, not bleached, and at least 1cm in length
• willing to NOT shave hair or have a very short haircut or apply bleach for the duration of the study
• has suitable venous access for consecutive blood draws

Exclusion criteria

• any health condition that may interfere with participation or the ability to provide informed consent, including any debilitating or life-threatening conditions;
• pregnancy or plans to become pregnant;
• liver cirrhosis or fulminant liver disease;
• known hypersensitivity reaction to doxycycline.
• detectable doxycycline in hair at enrollment.
• unable to provide a hair sample of ~50-100 strands of hair that are non-gray, not bleached, and at least 1cm in length
• does not have suitable venous access for consecutive blood draws