Doxi-Rio: Study on the Use of Doxycycline to Prevent Sexually Transmitted Infections in Rio de Janeiro

Brief summary (registry, in English)

The goal of this clinical trial is to learn if doxycycline post-exposure prophylaxis (doxy-PEP) can help prevent bacterial sexually transmitted infections (STIs) among sexual and gender minorities in Rio de Janeiro, Brazil, including men who have sex with men, transgender women, and travestis who are living with HIV or using HIV pre-exposure prophylaxis (PrEP). Bacterial STIs such as syphilis, gonorrhea, and chlamydia remain common in these populations, even with existing prevention strategies. This study aims to answer the following questions: whether doxy-PEP can reduce the number of new STIs, whether it is safe and well tolerated, whether participants use it as recommended, and whether its use may contribute to antibiotic resistance or changes in the body's natural bacteria. Doxy-PEP involves taking a dose of doxycycline, an antibiotic, shortly after sexual activity to reduce the risk of acquiring STIs. Participants will first receive information and counseling about doxy-PEP, including its possible benefits and risks, and will then choose whether or not to use this prevention strategy. Those who choose to use doxy-PEP will take doxycycline after sex as instructed and will be followed for up to 48 weeks, with clinic visits approximately every three months. During these visits, participants will be tested for STIs, monitored for side effects, and asked about medication use, sexual health, and overall well-being. Researchers will collect information on new STI diagnoses, safety, and how consistently participants use doxy-PEP. The study will also explore participants' experiences and perceptions of this strategy. The results of this study will help determine whether doxy-PEP is a practical and acceptable approach for STI prevention in Brazil and may inform future public health strategies.

What you commit to

• Study type: Interventional
• Planned participants: 200
• From 28 Oct 2025 to the primary completion date, 31 Oct 2027
• 1 site in 1 country
• Visits and tests: ask the trial team, the registry does not list them

Built from the registry fields of ClinicalTrials.gov. It describes the study, not your situation.

Who cannot take part

Copied verbatim from ClinicalTrials.gov and grouped by topic. Only the trial team decides who can take part.

Who the study is looking for

Age in the registry: 18 years to - · Sex: All · Accepts healthy volunteers

Full criteria on ClinicalTrials.gov

Sites (1)

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