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New research paper examines Doxycycline Postexposure Prophylaxis: A Promising Tool in the Fight Against STIs

A female nurse advises her patient on treatment options in the doctor's office.

A new paper published in The Journal of the American Medical Association examines the potential of doxycycline postexposure prophylaxis (doxyPEP) in reducing STI rates. Sexually transmitted infections (STIs) are a global health concern, with over 1 million treatable cases reported daily. While most bacterial STIs are treatable with antibiotics, challenges in prevention persist due to asymptomatic cases, limited healthcare access, and anonymous partners.

The paper’s co-authors include Kenneth Mayer, MD, Medical Research Director and Co-Chair of The Fenway Institute, Michael Traeger, PhD, postdoctoral research fellow in the Department of Population Medicine at Harvard Medical School and Harvard Pilgrim Health Care Institute, and Julia Marcus, PhD, MPH, Adjunct Faculty at The Fenway Institute and an Associate Professor in the Department of Population Medicine at Harvard Medical School and Harvard Pilgrim Health Care Institute.

Doxycycline, a safe and effective antibiotic, has been used for various purposes, including preventing chlamydia after sexual assault. Recent clinical trials have investigated its use as a postexposure prophylactic measure for STIs, particularly in populations at higher risk. Here are some key findings from the research:

  • Reduced Incidence of STIs: A study in France involving men who have sex with men (MSM) using antiretroviral preexposure prophylaxis (PrEP) found that a single 200-mg dose of doxycycline taken within 24 hours after condomless sex significantly reduced the incidence of first-incident STIs, including chlamydia and syphilis.
  • Positive Outcomes for HIV+ Individuals: In another study, people living with HIV using doxyPEP also experienced a decrease in STI rates, with significant reductions in chlamydia and gonorrhea cases.
  • High Adherence Rates: Participants in the clinical trials demonstrated strong adherence to the doxyPEP regimen, with over 85% reporting consistent usage.
  • Safety Profile: Doxycycline was generally well tolerated, with common side effects including diarrhea, sunburn, and nausea. Severe adverse events were rare.


However, concerns about antibiotic resistance and the potential impact on the host microbiome have been raised, although these issues did not surface in the current trials and further research is needed to assess the long-term effects of doxyPEP.

Despite these questions, several local and state health departments have started recommending doxyPEP for MSM and transgender women with a history of bacterial STIs. The Centers for Disease Control and Prevention is advocating shared decision-making between clinicians and patients to determine the appropriateness of doxyPEP and is in the process of developing guidelines.

While more research is needed, doxycycline postexposure prophylaxis has great potential as a valuable tool in combating the growing bacterial STI epidemic.

“Doxycycline Postexposure Prophylaxis and Sexually Transmitted Infections” is available here.

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