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Doxycycline Pill Study for STI Prevention

This study is looking into how well Doxycycline Pill (200mg dose) is absorbed by the body. Researchers want to understand why Doxycycline Post-exposure Prophylaxis (DoxyPEP), a way to prevent sexually transmitted infections (STIs), has worked in some groups but not others. You could be eligible if you are 18 or older, not currently at risk for an STI, and willing to use condoms for prevention. To see if the Doxycycline Pill is absorbed, researchers will measure the amount of the drug in your hair, blood, and urine after 4 weeks. The study is currently recruiting 48 participants.

Study design
This is an interventional study with 48 planned participants. It is a randomized study, meaning participants will be assigned to different groups by chance.
What's involved
You would need to provide hair, blood, and urine samples. The study measures will be taken at 4 weeks.
Compensation
Not stated in the trial record.
Follow-up
Your Doxycycline levels will be measured at 4 weeks after starting the intervention.

AI-generated from the public study record. Only the study team can confirm whether you're eligible — confirm details with them before making decisions.

NCT06414408

Randomized Directly Observed Therapy Study to Interpret Clinical Trials of Doxy-PEP

Recruiting
EARLY_PHASE1Ages 18+InterventionalBasic science
University of California, San Francisco
~48 participants
Updated 2026-04-13 on ClinicalTrials.gov
What's tested:Doxycycline Pill

At a glance

Recruiting sites
1 of 1 listed site is recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Hair Doxycycline Concentration
Measured over 4 weeks
+2 more outcomes measured

Conditions

Sexually Transmitted Diseases, Bacterial

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Bacterial InfectionSexually Transmitted Disorder

Where it's being run

1 sites across 1 states
California1

Study leadership

  • Matthew Spinelli, MD, MAS · PRINCIPAL_INVESTIGATOR · University of California, San Francisco

Who to contact

Shivani Mahuvakar
[email protected]
415-878-6384
Email the study team

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Eligibility criteria

Inclusion

not currently at risk of a sexually transmitted infection and willing to use other methods, such as condoms, for STI prevention;
if diagnosed with an STI in the past two years and/or a partner was diagnosed with an STI in the past year, is willing to use condoms for STI prevention;
willing to provide hair, blood, and urine samples;
not currently enrolled in other STI prevention studies;
able to speak English
transgender women participants should be currently using estrogen gender affirming hormone therapy with blood estrogen levels demonstrating consistent use
transgender men participants should be currently using testosterone gender affirming hormone therapy with blood testosterone levels demonstrating consistent use
able to provide a hair sample of \~50-100 strands of hair that are non-gray, not bleached, and at least 1cm in length
willing to NOT shave hair or have a very short haircut or apply bleach for the duration of the study
has suitable venous access for consecutive blood draws

Exclusion

any health condition that may interfere with participation or the ability to provide informed consent, including any debilitating or life-threatening conditions;
pregnancy or plans to become pregnant;
liver cirrhosis or fulminant liver disease;
known hypersensitivity reaction to doxycycline.
detectable doxycycline in hair at enrollment.
unable to provide a hair sample of \~50-100 strands of hair that are non-gray, not bleached, and at least 1cm in length
does not have suitable venous access for consecutive blood draws

What this trial measures

  • Hair Doxycycline Concentration4 weeks

    Doxycycline concentrations will be measured using liquid chromatography tandem mass spectrometry within hair samples for each of the four dosing patterns within an intensive washout pharmacokinetic phase following initial dosing.

  • Plasma Doxycycline Concentration4 weeks

    Doxycycline concentrations will be measured using liquid chromatography tandem mass spectrometry within plasma samples for each of the four dosing patterns within an intensive washout pharmacokinetic phase following initial dosing.

  • Urine Doxycycline Concentration4 weeks

    Doxycycline concentrations will be measured using liquid chromatography tandem mass spectrometry within urine samples for each of the four dosing patterns within an intensive washout pharmacokinetic phase following initial dosing.