A Phase 4 interventional study of On demand doxycycline hyclate 200mg and Daily doxycycline hyclate 100mg in Gonorrhea, Chlamydia and Syphilis, sponsored by University of California, Los Angeles. Not yet recruiting at 1 site in United States. Open to male participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-11-09.
Sponsored by University of California, Los Angeles · Phase 4, Interventional, and Prevention
The goal of this clinical trial is to learn if three different dosing strategies of doxycycline (daily, weekly, and on-demand) works to prevent sexually transmitted infections (gonorrhea, chlamydia, and syphilis) among men who use methamphetamine and who have sex with other men. The main question it aims to answer is:
Does daily, weekly, and on-demand doxycycline dosing strategies lower the incidence of quarterly STIs (gonorrhea, chlamydia, and syphilis)?
Participants will:
Take doxycycline either on-demand (within 72 hours after sex), daily, or weekly doxycycline for one year Visit the clinic once every 3 months to complete questionnaires, undergo HIV/STI testing, and collect samples. Additional visits may be needed to receive STI treatment.
Complete text surveys once every month
This study will evaluate the acceptability, effectiveness, and adherence of alternative doxycycline dosing strategies to optimize STI prophylaxis in this high-risk population. We will accomplish this through the following independent, yet interrelated Aims: 1) Determine effectiveness of fixed-dose daily, fixed-dose weekly, and event-driven dosing of doxycycline for STI prophylaxis; 2) Assess acceptability and preferences for doxycycline as STI prophylaxis through either fixed dose (daily or weekly) or event-driven (post-exposure) dosing strategies through individual interviews; 3) Evaluate and compare adherence and tolerability of daily, weekly, and event-driven doxycycline dosing strategies. We will conduct an open-label, non-inferior, randomized control trial (RCT) comparing fixed-dose daily, fixed-dose weekly, and event-driven doxycycline dosing strategies on quarterly incidence of STIs among MSM who use MA. We will screen 900 individuals to recruit a cohort of 300 MSM who self-report MA use in conjunction with condomless anal intercourse in the past month. At the Enrollment visit, participants will receive HIV, syphilis, and gonorrhea/chlamydia (GC/CT) testing as well as complete demographic and behavioral questionnaires. Enrolled participants will be randomly assigned 1:1:1 to either fixed-dose daily doxycycline (100mg daily; n=100), fixed-dose weekly doxycycline (200mg weekly; n=100), or event-driven doxyPEP (200mg taken up to 72 hours after a potential STI exposure; n=100; standard of care). All participants will participate in Quarterly follow-up visits where they will be assessed for HIV, bacterial STIs (GC/CT and syphilis), adherence to doxycycline, sexual behaviors/practices, substance use, nasal Staph aureus colonization and doxycycline resistance over 12 months. The primary outcome for this study will be quarterly incidence of, GC, CT, and/or early syphilis (defined as newly positive rapid plasma reagin [RPR] or four-fold rise in RPR titers), by arm.
167 studies on the registry are indexed under Gonorrhea; 31 are open to participants now.
This study's planned enrollment of 300 is below the median of 400 across 125 interventional studies indexed under Gonorrhea.
Browse Gonorrhea studies →University of California, Los Angeles is the lead sponsor of 1,170 studies on the registry; 195 are open to participants now.
Of its 95 completed or terminated interventional studies of FDA-regulated products, 70 (74%) have results posted.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants randomized to on-demand doxycycline will be instructed to take doxycycline hyclate 200mg once as needed within 24 and up to 72 hours after sex (not to exceed 200mg in 24 hours).
Drug: On demand doxycycline hyclate 200mg
Participants randomized to receive fixed dose weekly doxycycline hyclate 200mg will be instructed to take doxycycline hyclate 200mg once weekly, regardless of sexual exposure.
Drug: Weekly doxycycline hyclate 100mg
Participants randomized to receive fixed dose daily doxycycline hyclate 100mg will be instructed to take doxycycline hyclate 100mg once daily, regardless of sexual exposure.
Drug: Daily doxycycline hyclate 100mg
Participants randomized to receive on-demand doxycycline hyclate 200mg will be instructed to take doxycycline hyclate 200mg once as needed within 24 hours and up to 72 hours after sex (not to exceed 200mg in 24 hours)
Participants randomized to receive fixed dose daily doxycycline hyclate 100mg will be instructed to take doxycycline hyclate 100mg once daily
Participants randomized to receive weekly doxycycline hyclate 100mg will be instructed to take doxycycline hyclate 100mg once weekly
Quarterly incidence of chlamydia, gonorrhea, and/or early syphilis infection
Time frame: Quarterly incidence of C. trachomatis, N. gonorrhoeae, and/or early syphilis infection by laboratory-based diagnosis (over 1 year time period)
Plan to share: Yes
No publications or documents are linked to this record.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is not yet recruiting, as verified in Nov 2026. You cannot join it, but the record below documents what was studied.
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