Doxycycline to prevent bacterial STIs in sexual and gender minorities in Rio de Janeiro.
Official title: Doxi-Rio: Pilot Implementation of Post-exposure Prophylaxis for Sexually Transmitted Infections With Doxycycline in Rio de Janeiro, Brazil
Run by Oswaldo Cruz Foundation · NCT07500415 · Data updated 2026-11-12
This research will try taking doxycycline after sex to see if it lowers the chance of syphilis, gonorrhea, and chlamydia for men who have sex with men, transgender women, and travestis in Rio de Janeiro who are living with HIV or using PrEP.
Quick facts
| Study type | Interventional |
|---|---|
| Ages | 18 Years and up |
| Sex | All |
| Enrollment | 200 (estimated) |
| Sponsor | Oswaldo Cruz Foundation Academic / other |
| Locations | 1 site (Rio de Janeiro, Rio de Janeiro) |
| Status | Recruiting |
| Started | October 28, 2025 |
| Main results expected | October 2027 |
| Study ends | May 2028 |
| Registry record updated | March 30, 2026 |
| Trial ID | NCT07500415 on ClinicalTrials.gov |
Is this trial a fit for you?
✓Likely a good fit
Adults (≥18) assigned male at birth, transgender women, or travestis who have sex with men, are living with HIV or have used PrEP for at least six months, and who had at least one bacterial STI in the past 12 months are the intended candidates.
✕Probably not a fit
People with a known allergy to doxycycline, those taking contraindicated medications, or individuals who are not in the specified populations or who lack a recent STI history are unlikely to benefit from participation.
A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.
What this trial studies
This interventional trial tests doxycycline post-exposure prophylaxis (doxy-PEP) taken shortly after sexual activity among sexual and gender minorities in Rio de Janeiro, including men who have sex with men, transgender women, and travestis who are living with HIV or using PrEP. Participants receive counseling about doxy-PEP and are instructed on when to take a dose after potential exposures, with regular clinic visits for symptom checks and laboratory STI testing. The study tracks new cases of syphilis, gonorrhea, and chlamydia as primary outcomes, and also monitors safety, adherence, and potential effects on antibiotic resistance and the body’s normal bacterial flora. People with doxycycline allergy or taking contraindicated medications are excluded.
Why it matters
Potential benefit: If successful, doxy-PEP could substantially reduce rates of bacterial STIs in these high-risk communities.
How similar studies have gone: Previous trials among men who have sex with men have shown doxy-PEP can substantially reduce bacterial STIs, though those studies have also raised concerns about potential antimicrobial resistance.
Who can join: the full rules
Show full inclusion / exclusion criteria
Inclusion Criteria: * Individuals assigned male at birth (cisgender or transgender men), transgender women, or travestis who have sex with men * Age ≥18 years * Living with HIV or currently using HIV pre-exposure prophylaxis (PrEP) for at least 6 months * History of at least one bacterial sexually transmitted infection (chlamydia, gonorrhea, or syphilis) in the past 12 months (laboratory-confirmed or self-reported) * Willing and able to provide informed consent Exclusion Criteria: * Known allergy or hypersensitivity to doxycycline or other tetracycline-class antibiotics * Current use of medications that may significantly interact with doxycycline or are contraindicated, including systemic retinoids, barbiturates, carbamazepine, or phenytoin
Where it's running
-
Instituto Nacional de Infectologia Evandro Chagas
Rio de Janeiro, Rio de Janeiro, Brazil Recruiting
Study contacts
- Study coordinator: Beatriz Grinsztejn, PhD
- Email: beatriz.grinsztejn@gmail.com
- Phone: +55 2138659128
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How to take part
- Review the eligibility criteria above with your treating physician.
- Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
- Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.