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Study identifier: NCT07500415 Synced from ClinicalTrials.gov · July 29, 2026
● Recruiting

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

Condition: Sexually Transmitted Diseases · Syphilis · Gonorrhea  ·  Sponsor: Oswaldo Cruz Foundation

PhaseNA
Planned participants200
Who can joinAll sexes, 18 Years to no upper limit
Healthy volunteersYes

About this study

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, …

This description comes directly from the study's public registry record.

Talk to the study team

Beatriz Grinsztejn, PhD  ·  +55 2138659128  ·  beatriz.grinsztejn@gmail.com

Always discuss trial participation with your own doctor first.

Locations (1)

Instituto Nacional de Infectologia Evandro ChagasRio de Janeiro, Rio de Janeiro, BrazilRecruiting

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Source record: clinicaltrials.gov/study/NCT07500415