DoxyPEP meaning: what the name stands for
DoxyPEP stands for doxycycline post-exposure prophylaxis. Put simply: you take the antibiotic doxycycline after sex, to prevent an infection instead of treating one later.
You take one dose of 200 mg (two tablets of 100 mg) after sex without a condom. Ideally within 24 hours, and no later than 72 hours. It is not a daily pill: you only take it when you had a risk.
How does doxyPEP work?
Syphilis, chlamydia and gonorrhoea are caused by bacteria. After sex it takes a while before those bacteria have multiplied enough to cause an infection. DoxyPEP uses that window.
Doxycycline stops bacteria from making the proteins they need to grow. When you take it within 72 hours, the antibiotic reaches the bacteria while there are still only a few of them. That makes it much harder for an infection to take hold.
That is also why timing matters: the sooner you take it, the fewer bacteria there are to stop. Use the calculator on the doxyPEP dosage page to see how much time you have left.
What does doxyPEP protect against?
In the large DoxyPEP study, published in 2023 in the New England Journal of Medicine, the group that used doxyPEP had about two thirds fewer bacterial STIs than the group that did not.
Syphilis
Chlamydia
Gonorrhoea
HIV, herpes, HPV
DoxyPEP works less well against gonorrhoea because many gonorrhoea strains are already resistant to this type of antibiotic. It does nothing against viruses such as HIV, herpes, HPV, mpox or hepatitis. For HIV you need PrEP, HIV PEP or condoms.
Who is doxyPEP for?
Most research was done among gay and bisexual men and trans women who have sex without a condom and had an STI in the past year. That is also the group for whom health authorities such as the US CDC recommend doxyPEP, in guidelines published in 2024.
- You regularly have sex without a condom with different partners.
- You had syphilis, chlamydia or gonorrhoea in the past year.
- You use PrEP or live with HIV and want extra protection against bacterial STIs.
And women? A study among cisgender women in Kenya did not show a clear effect. Researchers think this may be partly because not everyone took the tablets. Read more in doxyPEP for women.
Is doxyPEP the same as doxycycline?
The medicine is exactly the same: doxycycline, an antibiotic that doctors have prescribed for decades for infections such as chlamydia, acne and Lyme disease. What makes it doxyPEP is how you use it: one dose of 200 mg after sex, to prevent an infection.
You may see two names on the box: doxycycline hyclate and doxycycline monohydrate. Both work for doxyPEP, at the same dose.
DoxyPEP and antibiotic resistance
Every antibiotic can help bacteria become resistant. That is why doxyPEP is meant for people with a real risk of STIs, and only after sex, not as a daily habit. Researchers keep a close eye on resistance, especially in gonorrhoea and in bacteria that normally live on your skin and in your gut.
What you can do: only take a dose when you had a risk, never more than 200 mg in 24 hours, and keep testing so infections are found and treated properly.
What doxyPEP is not
Not PrEP
It does not protect against HIV.
Not a treatment
Symptoms? Get tested and treated.
Not a daily pill
Only after sex without a condom.
Not a test
Keep testing every 3 months.
