A San Francisco sexual health clinic significantly reduced rates of bacterial sexually transmitted
infections (STIs) among patients by preemptively prescribing the antibiotic doxycycline for use
after unprotected sex (DoxyPEP).

The study, which appeared in the August edition of the journal Sexually Transmitted Infections, focused on patients who take pre-exposure prophylaxis (PrEP), a medication that protects HIV-negative people from contracting the virus. 

People who take PrEP tend to be at greater risk of contracting bacterial STIs, and researchers found that, among these patients, DoxyPEP (post-exposure prophylaxis) reduced the rate of new infections by 58%.

While randomized clinical trials of DoxyPEP have produced similar results, this study was among the first to test the intervention in a real-world setting.

All PrEP clients at the San Francisco AIDS Foundation Sexual Health Clinic have quarterly HIV and bacterial STI screening. As part of that routine care, the clinic began offering DoxyPEP to anyone who takes PrEP in November 2022. DoxyPEP is prescribed for use within 72 hours of unprotected sex.

Among the 1,209 PrEP patients who opted to take DoxyPEP, there was a 78% reduction of syphilis cases and a 67% reduction in chlamydia.

Also, researchers did not measure antimicrobial resistance, a growing public health concern in
which overuse of antibiotics threatens the effectiveness of these medications.