Daily doxycycline use to study its effects on preventing sexually transmitted infections

Daily Doxy: Study of Persons Receiving Daily Doxycycline to Inform Sexually Transmitted Infection Prophylaxis Regimens

Phase 4 Interventional Emory University · NCT06545656

This study is testing whether taking doxycycline every day for a week can help prevent sexually transmitted infections by looking at how the drug works in the body.

Quick facts

PhasePhase 4
Study typeInterventional
Enrollment20 (estimated)
Ages18 Years to 59 Years
SexAll
SponsorEmory University Academic / other
Drugs / interventionsChemotherapy, radiation
Locations1 site (Atlanta, Georgia)
Trial IDNCT06545656 on ClinicalTrials.gov

What this trial studies

This project aims to gather data on how daily doses of doxycycline affect drug concentrations in mucosal tissues over a week in individuals assigned male or female sex at birth. Participants will take doxycycline daily for seven days, with samples collected afterward to analyze drug levels in the body. The study builds on previous research that explored single-dose doxycycline for STI prevention, focusing on the pharmacokinetics of daily dosing. The findings will help inform future prophylaxis strategies against bacterial sexually transmitted infections.

Who should consider this trial

Good fit: Ideal candidates include healthy individuals assigned male or female sex at birth who are not currently taking doxycycline or other tetracycline-derived antibiotics.

Not a fit: Patients with chronic liver disease or those requiring immunomodulatory medications may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could enhance prophylactic measures against bacterial sexually transmitted infections, potentially reducing their incidence.

How similar studies have performed: Previous studies have shown promise with single-dose doxycycline for STI prevention, but this approach of daily dosing is relatively novel.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Assigned male sex or female sex at birth
* In good general health
* Not currently taking doxycycline or other tetracycline-derived antibiotics and no plans to initiate during the study
* For HIV positive people, on stable antiretroviral therapy with an undetectable viral load and cluster of differentiation 4 (CD4) count\> 300ul/ml
* Willing to use condoms consistently for the duration of the study
* Able to provide informed consent
* No plans for relocation in the next 4 months
* Not pregnant and does not plan on getting pregnant for the duration of the study
* Willing to undergo peripheral blood, urine, rectal or vaginal secretion collection, and a rectal or vaginal and cervical biopsy procedure
* Willing to use study products as directed

Exclusion Criteria:

* Current or chronic history of liver disease
* Continued need for, or use during the 90 days prior to enrollment, of the following medications:

  * Systemic immunomodulatory agents
  * Supraphysiologic doses of steroids (short course steroids less than 7 days duration, allowable at the discretion of the investigators)
  * Chemotherapy or radiation for treatment of malignancy
  * Experimental medications, vaccines, or biologicals
* Intent to use doxycycline or other tetracycline-derived antibiotics during the course of the study, outside of the study procedures
* Any other clinical condition or prior therapy that, in the opinion of the investigator, would make the patient unsuitable for the study or unable to comply with the study requirements
* Known allergic reaction to study drugs
* Significant laboratory abnormalities at baseline visit for rectal biopsies, including but not limited to:

  * Hemoglobin (Hgb) ≤ 10 g/dL
  * Partial thromboplastin time (PTT) \> 1.5x upper limit of normal (ULN) or international normalised ratio (INR) \> 1.5x ULN
  * Platelet count \<100,000

Where this trial is running

Atlanta, Georgia

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions Sexually Transmitted Infection
Last reviewed 2026-06-15 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.