NIH Study Finds That Post-Exposure Doxycycline Reduces STI Rate

An article published in the New England Journal of Medicine found that post-exposure doxycycline reduces sexually transmitted infection (STI) rates by two-thirds. The study found that men who have sex with men (MSM) and transgender women had significantly lower rates of chlamydia, gonorrhea, and syphilis when given doxycycline within 72 hours of condomless sex.

The open-label, randomized study recruited MSM and transgender women who were already taking preexposure prophylaxis (PrEP) for HIV and those who were living with HIV. All patients had gonorrhea, chlamydia, or syphilis in the year before the study began.

Researchers divided the 501 patients into two groups, assigning two-thirds to take 200 mg of doxycycline, a widely used antibiotic, within 72 hours of condomless sex and the remaining one-third to standard care without doxycycline. Patients were screened for STIs quarterly to monitor infection rates.

Among the participants taking PrEP and assigned to the experimental group, 10.7% were diagnosed with STIs during their quarterly screening. Meanwhile, those taking PrEP and assigned to standard care had a higher rate of STI infection at 31.9%.

A deeper analysis into the rates of each individual infection determined that patients on PrEP assigned to the doxycycline group had a 55% lower risk of gonorrhea. Additionally, patients had an 88% lower risk of chlamydia and an 87% lower risk of syphilis.

For patients living with HIV infection, the STI rate with post-exposure doxycycline was 11.8%. Comparatively, those living with HIV and assigned to standard care protocols had significantly higher rates of infection at 30.5%.

Focusing on the statistics for each type of STI, the data revealed that people living with HIV had a 57% lower risk of gonorrhea under the post-exposure doxycycline protocol. Similarly, the rates of chlamydia and syphilis were 74% and 77%, respectively.

“Given its demonstrated efficacy in several trials, doxy-PEP should be considered as part of a sexual health package for men who have sex with men and transwomen if they have an increased risk of STIs,” according to Annie Luetkemeyer, MD, professor of infectious diseases at Zuckerberg San Francisco General Hospital at UCSF, and co-principal investigator of the study, in the NIH release. “It will be important to monitor the impact of doxy-PEP on antimicrobial resistance patterns over time and weigh this against the demonstrated benefit of reduced STIs and associated decreased antibiotic use for STI treatment in men at elevated risk for recurrent STIs.”

As concerns about STI rates rise, it is critical to have preventive tools and effective screening methods to minimize the rates of infection and their associated risks.