A Phase 4 interventional study of Doxycycline (200mg/day) in Syphilis Infection, Gonorrhea and Chlamydia, sponsored by Bangrak STIs Center. Recruiting at 1 site in Thailand. Open to male participants aged 18 Days to 60 Days, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-02-09.
Sponsored by Bangrak STIs Center · Phase 4, Interventional, and Prevention
The objective of this research is to evaluate the efficacy and safety of doxycycline in MSM for preventing sexually transmitted infections (gonorrhea, chlamydia, and syphilis) in Thailand
Participation in this study will last approximately 12 weeks and will include 2-3 clinic visits, along with 10-11 follow-up phone contacts over a period of 11 weeks.
167 studies on the registry are indexed under Gonorrhea; 31 are open to participants now.
This study's planned enrollment of 400 is close to the median of 400 across 125 interventional studies indexed under Gonorrhea.
Browse Gonorrhea studies →This is the only study on the registry with Bangrak STIs Center as lead sponsor.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Biological male, aged not over 60 years
Thai nationality
Able to read, communicate, and understand the Thai language
Men who have sex with men (MSM), aged 18 years or older and not over 60 years
Having at least one of the following risk factors:
A history of condomless sex, or condom failure (breakage, leakage, or slippage), via any sexual route with at least two sexual partners within the past 3 months
A diagnosis of gonorrhea, chlamydia, or syphilis within the past 6 months
Current use of pre-exposure prophylaxis (PrEP)
Willing and able to participate in study procedures (e.g., able to return to the clinic for scheduled testing for gonorrhea, chlamydia, and syphilis; able to complete doxycycline use records; and able to receive follow-up phone calls from the research team)
Willing and able to provide written to participate in the study
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Exclusion Criteria:
Diagnosed with syphilis and not yet treated, or currently receiving treatment with benzathine penicillin G or doxycycline
Receipt of benzathine penicillin G within the past 12 weeks
Prior receipt of a gonorrhea vaccine
Current use of medications or products that may interact with doxycycline, including:
Vitamin A derivatives (e.g., isotretinoin, acitretin)
Antiepileptic drugs (e.g., phenytoin, carbamazepine, phenobarbital)
agents (e.g., methotrexate)
Medications for heart failure or cardiac arrhythmias (e.g., digoxin)
Anticoagulants (e.g., warfarin)
Use of oral or injectable medications that affect blood cells, such as anticancer drugs, chemotherapy, systemic , or targeted therapies
History of renal impairment ( \< 60 mL/min/1.73 m²) or hepatic impairment ( or ALT > 3 times the )
Uncontrolled or unstable underlying diseases, such as hematologic disorders, cancer, diseases, or neurological disorders
Severe medical or psychiatric conditions that, in the investigator's judgment, may increase study-related risk or impair the participant's ability to provide
Alcohol dependence (inability to control alcohol consumption, withdrawal symptoms upon reduction or cessation, or continued use despite harm) or illicit drug dependence (regular, uncontrolled use) within the past 12 months prior to enrollment, which may affect doxycycline use for STI prevention
Previous participation in this study with prior randomization
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.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
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.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
GFR and eGFR (kidney filtering)
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ALT and AST (liver enzymes)
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ULN (upper limit of normal)
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive DoxyPEP for STIs prophylaxis in this arm
Drug: Doxycycline (200mg/day)
Participants will receive standard STIs prevention
Drug page: Doxycycline
Doxycycline 200 mg single dose after unprotected sex within 24-72 hours
To evaluate the efficacy of doxycycline in preventing sexually transmitted infections (gonorrhea, chlamydia, and syphilis) among men who have sex with men in Thailand.
Measure the proportion of participants who test positive by NAAT for gonorrhea or chlamydia at any anatomical site (genital, pharyngeal, or rectal), or who are diagnosed with syphilis during the study period.
Time frame: 12 weeks
Plan to share: No — Individual participant data (IPD) from this study will not be publicly shared due to ethical and legal considerations. The study involves sensitive sexual health information from key populations, and even de-identified datasets may carry a risk of re-identification. Data sharing is also subject to Thai data protection regulations and the conditions approved by the institutional ethics committee and participant informed consent.
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
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Studies of the drug tested here: Doxycycline