A hand holding a DoxyPEP pill, with a black background and gold and white text about DoxyPEP's role in bacterial STI prevention.

DoxyPEP

Bacterial STI Prevention After Unprotected Sex

DoxyPEP stands for Doxycycline Post-Exposure Prophylaxis. It is an STI prevention strategy where doxycycline, an antibiotic, is taken after unprotected sex to reduce the risk of certain bacterial sexually transmitted infections.

DoxyPEP is not HIV PrEP and does not prevent HIV. It is designed to help reduce the risk of acquiring Syphilis, Chlamydia, and, in some studies, Gonorrhea after possible exposure.

How Effective Is DoxyPEP?

Clinical trials reviewed by the CDC found that 200 mg of doxycycline taken within 72 hours after unprotected sex reduced:

  • Syphilis and chlamydia by more than 70%

  • Gonorrhea by approximately 50%

Effectiveness depends on proper timing, appropriate patient selection, and continued STI screening.

Who May Benefit from DoxyPEP?

CDC recommends that healthcare providers discuss DoxyPEP with:

Gay, bisexual, and other men who have sex with men, and transgender women who have had syphilis, chlamydia, or gonorrhea within the past 12 months.

DoxyPEP may also be considered through shared decision-making for some individuals with ongoing higher-risk sexual exposures, even if they have not had a recent STI. Evidence is more limited in other populations, including cisgender women, heterosexual cisgender men, transgender men, and some nonbinary individuals assigned female at birth.

How Is DoxyPEP Taken?

The recommended dose is:

Doxycycline 200 mg by mouth in one single dose as soon as possible after unprotected sex, ideally within 24 hours, and no later than 72 hours after oral, vaginal, or anal sex.

Do not take more than:

200 mg in a 24-hour period.

Your provider should prescribe an amount based on your expected need until your next follow-up visit.

Important Safety Considerations

DoxyPEP is not for everyone. It should be prescribed after a clinical review of your health history, medications, allergies, and STI risk profile.

Important considerations include:

  • Do not use if you have a doxycycline or tetracycline allergy.

  • Discuss use if pregnant, trying to become pregnant, or breastfeeding.

  • Separate doxycycline from calcium, iron, magnesium, antacids, and some supplements because they can reduce absorption.

  • DoxyPEP does not prevent viral infections such as HIV, herpes, HPV, mpox, or hepatitis.

  • Ongoing antibiotic resistance monitoring remains important, especially for gonorrhea and other bacteria. The CDC notes short-term harms appear low, but long-term resistance considerations remain under study.