A Phase 4 interventional study of Doxycycline in Sexually Transmitted Infection, sponsored by Emory University. Completed at 1 site in United States. Open to participants aged 18 Years to 59 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-05-01.
Sponsored by Emory University · Phase 4, Interventional, and Basic science
The goal of this project is to collect data regarding the concentrations of doxycycline in mucosal tissues after daily dosing for 7 days in people assigned male sex at birth (AMAB) and assigned female sex at birth (AFAB) to inform future studies of doxycycline to protect against bacterial sexually transmitted infections (STIs).
Recent studies have demonstrated the potential utility of single-dose oral doxycycline postexposure prophylaxis (Doxy-PEP) against bacterial sexually transmitted infections (STIs). Additional dosing strategies are being explored that would also provide protection from bacterial STIs. However, the pharmacokinetics of daily doxycycline and specifically the effect of this dosing on effective drug levels in mucosal tissues is underexplored. A previous pilot study conducted by the Division of human immunodeficiency virus (HIV) Prevention (DHP) Laboratory Branch at the Centers for Disease Control and Prevention (CDC) examined the ability of a single 100mg oral dose of doxycycline to penetrate the vaginal and rectal mucosa. However, data regarding daily doxycycline doses and accumulation of doxycycline with multiple doses are lacking.
The purpose of this project is to collect data regarding the ability of daily oral doxycycline taken for 7 days to concentrate in mucosal tissues in people assigned male sex at birth (AMAB) and assigned female sex at birth (AFAB). Results from this study will be compared to results of the previous pilot studies conducted by the DHP Laboratory Branch at CDC.
Healthy people assigned male or female sex at birth will take the first dose of doxycycline during the enrollment visit (Hour -144/Day -6) then will take the next 5 doses at home, one per day for the next 5 days. After 6 consecutive days of dosing, study participants will have samples collected (Hour 0/Day 0) and then will take the final dose. Rectal and vaginal swab samples will be obtained 2 to 4 hours after the final dose of doxycycline. Rectal and vaginal biopsy tissue will be collected 24 hours after the last dose.
424 studies on the registry are indexed under Sexually Transmitted Diseases; 71 are open to participants now.
This study's enrollment of 24 is below the median of 470 across 346 interventional studies indexed under Sexually Transmitted Diseases.
Browse Sexually Transmitted Diseases studies →Emory University is the lead sponsor of 1,386 studies on the registry; 236 are open to participants now.
Of its 229 completed or terminated interventional studies of FDA-regulated products, 174 (76%) have results posted.
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Exclusion Criteria:
Continued need for, or use during the 90 days prior to enrollment, of the following medications:
Significant laboratory abnormalities at baseline visit for rectal biopsies, including but not limited to:
Study participants taking 7 consecutive, daily doses of 100mg of Doxycycline.
Drug: Doxycycline
Doxycycline (DOX) will be given orally at 100mg doses. Participants will take the study medication for 7 consecutive days.
Also known as: Doxy-100, Oracea, Monodox
Doxycycline Concentration in Rectal Tissue
Rectal tissue doxycycline concentrations collected 24 hours after 7 daily (T7) doses of 100 mg of doxycycline were determined in assigned male sex at birth (AMAB) participants.
Time frame: 24 hours after last dose (Hour 24/Day 1)
Doxycycline Concentration in Vaginal Tissue
Vaginal tissue doxycycline concentrations collected 24 hours after 7 daily (T7) doses of 100 mg of doxycycline were determined in Assigned female sex at birth (AFAB) participants.
Time frame: 24 hours after last dose (Hour 24/Day 1)
Participants were recruited from the Hope Clinic in Atlanta, Georgia, USA. Participant enrollment began September 13, 2024, and all follow up was completed by April 29, 2025.
| Milestone | Doxycycline |
|---|---|
| Started | 24 |
| Completed | 23 |
| Not completed | 1 |
| Withdrew: Lost to follow-up | 1 |
Rectal tissue doxycycline concentrations collected 24 hours after 7 daily (T7) doses of 100 mg of doxycycline were determined in assigned male sex at birth (AMAB) participants.
| µg/g | Doxycycline |
|---|---|
| Doxycycline Concentration in Rectal Tissue | 2.330 (0.920 to 6.540) |
Vaginal tissue doxycycline concentrations collected 24 hours after 7 daily (T7) doses of 100 mg of doxycycline were determined in Assigned female sex at birth (AFAB) participants.
| µg/g | Doxycycline |
|---|---|
| Doxycycline Concentration in Vaginal Tissue | 1.320 (0.770 to 2.090) |
Collected over Information on adverse events was collected from the time participants provided consent to join the study (Screening Visit) until the final study visit occurring 7 days after the 7th dose of the study intervention (up to 56 days).. Non-serious events are listed at a 0% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Doxycycline | 0/24 (0%) | 0/24 (0%) | 0/24 (0%) |
| Age, Categorical(Participants) | Doxycycline |
|---|---|
| <=18 years | 0 |
| Between 18 and 65 years | 24 |
| >=65 years | 0 |
| Sex: Female, Male(Participants) | Doxycycline |
|---|---|
| Female | 11 |
| Male | 13 |
| Ethnicity (NIH/OMB)(Participants) | Doxycycline |
|---|---|
| Hispanic or Latino | 3 |
| Not Hispanic or Latino | 21 |
| Unknown or Not Reported | 0 |
| Race (NIH/OMB)(Participants) | Doxycycline |
|---|---|
| American Indian or Alaska Native | 0 |
| Asian | 1 |
| Native Hawaiian or Other Pacific Islander | 0 |
| Black or African American | 17 |
| White | 3 |
| More than one race | 3 |
| Unknown or Not Reported | 0 |
| Region of Enrollment(Participants) | Doxycycline |
|---|---|
| United States | 24 |
Documents are hosted by the registry — open the source record to download them.
Plan to share: Yes — De-identified individual participant data underlie the results published for this study (including text, tables, figures, and appendices) will be made available for sharing with other researchers.
Supporting information: Study protocol, Sap
This study is completed, as verified in Jun 2025. You cannot join it, but the record below documents what was studied.
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