Could an antibiotic taken after unprotected sex prevent STIs? What to know about doxy-PEP.

If approved, a new way of administering the antibiotic doxycycline — called doxy-PEP — could help protect people who are at high risk of STIs.  (Image credit: Shutterstock)

The U.S. is currently facing a surge in sexually transmitted infections (STIs). To address that rise, doctors have raised the possibility of prescribing some people an antibiotic to take after risky sexual encounters to prevent such infections.

The drug regimen, known as doxy-PEP, uses an old antibiotic called doxycycline and may reduce the risk of developing three major STIs — syphilis, gonorrhea and chlamydia — in people who are at high risk of repeated infection, evidence suggests. The Centers for Disease Control and Prevention (CDC) is currently evaluating these data and is expected to announce new guidance this summer. If that goes through, the FDA may expand the list of ways the doxycycline should be prescribed to include post-exposure prophylaxis (PEP) in certain populations.