The short version
CDC recommends that healthcare providers discuss doxycycline post-exposure prophylaxis (doxy PEP) with gay, bisexual and other men who have sex with men and transgender women who had syphilis, chlamydia or gonorrhea diagnosed in the previous 12 months. The decision is meant to be made with a healthcare provider after discussing benefits, downsides and the person’s health history.
Doxy PEP
A strategy intended to lower the chance of certain bacterial STIs after sex for selected people who meet CDC guidance.
HIV PEP
Emergency HIV-prevention medication after a possible HIV exposure. HIV PEP has its own 72-hour deadline and usually involves a 28-day course when prescribed.
What does the CDC guideline say?
The CDC guideline describes a 200 mg dose of doxycycline taken as soon as possible within 72 hours after oral, vaginal or anal sex, not exceeding 200 mg in 24 hours, for the population covered by the recommendation. That does not mean everyone should start doxy PEP. A clinician should review whether it makes sense for you, including possible side effects, medication interactions and concerns about antibiotic resistance.
What can doxy PEP help prevent?
CDC reports strong reductions in syphilis and chlamydia in clinical trials and a more modest reduction in gonorrhea. It does not prevent HIV, herpes, HPV, hepatitis or every other infection.
Does taking doxy PEP replace STI testing?
No. CDC recommends bacterial STI testing at the body sites exposed at baseline and every 3–6 months for people using doxy PEP, with ongoing review of whether the strategy is still appropriate.
What should I ask a provider?
- Does my recent STI history fit current CDC guidance?
- What side effects or medication interactions matter for me?
- How often should I be screened for STIs?
- Should I also consider HIV PrEP?
PrEP vs HIV PEP → STI testing guide
This page is general education, not personal medical advice. It summarizes current CDC guidance and does not tell any individual person to start an antibiotic.