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

Oswaldo Cruz Foundation

Status: Enrolling

Conditions: Sexually Transmitted Diseases; Gonorrhea; Syphilis; Chlamydia Infections; HIV Infections

Treatments: Drug: Doxycycline

Study type: Interventional

Funder types: Other

Identifiers

NCT07500415

87288525.2.0000.5262

Details and patient eligibility

About

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.

Enrollment: 200 estimated patients

Sex: All

Ages: 18+ years old

Volunteers: Accepts Healthy Volunteers

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

Trial design

Primary purpose: Treatment

Allocation: N/A

Interventional model: Single Group Assignment

Masking: None (Open label)

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200 participants in 1 patient group

Doxycycline Post-Exposure Prophylaxis (Doxy-PEP)

Experimental group

Description:

Participants who choose to initiate doxycycline post-exposure prophylaxis (doxy-PEP) after receiving counseling on its risks and benefits. Participants will take doxycycline after sexual activity as instructed and will be followed for up to 48 weeks with regular clinical visits, including testing for sexually transmitted infections, safety assessments, and adherence evaluation. Participants who initially decline doxy-PEP may choose to initiate it at any time during the study.

Treatment:

Drug: Doxycycline