Q&A: What does the latest research say about doxycycline prophylaxis for bacterial STIs?
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Key takeaways:
- Doxy-PEP continues to show positive impacts in trials when taken within 3 days of having condomless sex.
- Some questions surrounding resistance and doxy-PEPs benefits for cisgender women remain.
In recent years, cases of sexually transmitted infections such as chlamydia, gonorrhea and syphilis have been rising in the United States, affecting all populations and prompting additional prevention efforts.
One preventative, doxycycline post-exposure prophylaxis (doxy-PEP), has been shown to reduce new cases of chlamydia, gonorrhea and syphilis if a single dose is taken within 3 days of having condomless sex. An unfortunate finding in a recent study of doxy-PEP, however, showed that it may not work for cisgender women and experts have not been able to pinpoint exactly why.
Healio spoke with Aniruddha Hazra, MD, associate professor and director of the infectious disease fellowship program at the University of Chicago and medical director of the UCM Sexual Wellness Clinic, about a recent paper he and colleagues published reviewing the latest research on doxy-PEP.
Healio: What prompted this paper?
Hazra: Since the last review of the topic in 2020, there have been multiple large trials further studying the safety and efficacy of this intervention. Now with most health agencies providing guidance around doxy-PEP, we felt an updated review was needed to help clinicians and patients understand its benefits and limitations in 2024.
Healio: Are there new resistance data?
Hazra: We have updated data on antimicrobial resistance (AMR) from two large doxy-PEP studies (DOXYPEP & DOXYVAC) examining AMR within gonococcal isolates, as well as patient flora. Data demonstrates high tetracycline resistance of N. gonorrhoeae isolates at baseline which limits our ability to detect significant changes of gonococcal AMR between those on doxy-PEP and those without.
Of note, doxy-PEP does not appear to have a significant effect on normal flora in the short term. However, we need more data, particularly longitudinal, to better understand its overall impact on AMR.
Healio: Is there any more information on why doxy-PEP was not effective among cisgender women? Was it adherence or biological?
Hazra: There is not a clearcut biological reason why doxy-PEP should not be effective in cisgender women. Although subjective measures noted adherence to doxy-PEP to be adequate, objective measures of doxycycline use suggest a different story. We ultimately need more doxy-PEP studies, including of cisgender women and people assigned female at birth of all genders to provide better data on its effectiveness.
Healio: What is the clinical take-home message?
Hazra: Doxy-PEP has the potential to significantly decrease bacterial STIs among high-burden populations. We need to study its population-level impact while implementing this intervention in real time. By delaying doing so, we risk making the same mistakes made with HIV PrEP.
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