This study is being conducted to better understand how doxycycline behaves in the body and to compare dosing schedules’ effects on absorption and safety.

You may be eligible for this study if you meet the following criteria.

Inclusion Criteria:

• Have natural, untreated hair (e.g., has not been bleached, permed, relaxed, dyed/colored)
• Ages 18-65
• Willing to participate in video-based communications with study staff by using a smartphone or laptop
  
  

Exclusion Criteria:

• Major, unstable medical conditions that would impact study participation
• Living with HIV
• Currently pregnant, breastfeeding, or planning to get pregnant soon
• Current bacterial STI (e.g., chlamydia, gonorrhea, syphilis)

• Complete a screening visit to determine eligibility
• If eligible, you will be randomly assigned to a study group
• Take doxycycline as directed (immediate-release or delayed-release)
• Attend approximately 17 study visits over about 37 days (some may be completed via video)
• Provide samples such as blood, urine, hair, and other body fluids for research
• Undergo HIV and STI testing, physical exams, and receive counseling
• Take study medication under observation, either in clinic or via video

Participants may receive up to $2,190 for completing all study visits and procedures. Transportation support is available, including rideshare services for those without transportation and parking validation for those who drive. Travel compensation may be provided for participants traveling more than 50 miles, and snacks or meals may be offered during longer visits.

There is no cost for you to participate in our research study.