DoxyPEP, STI Prevention

Two 100 mg of doxycycline should ideally be taken within 24 hours, but no later than 72 hours after condomless sex. Condomless sex means oral, anal, or vaginal/front-hole sex where a condom is not used for the entire time.

If you have sex again within 24 hours of taking doxycycline, take another dose 24 hours after your last dose. You can take doxycycline as often as every day when you are having condomless sex but do not take more than 200 mg (two 100 mg pills) every 24 hours.

Take doxycycline with plenty of water or something else to drink so that it does not get stuck when you swallow. If your stomach is upset by doxycycline, taking it with food may help.

• Some people are more sensitive to the sun when they take doxycycline, so wear sunscreen.
• Please do not share doxycycline with others.
• Avoid dairy products, calcium, antacids, or multivitamins 2 hours before and after taking doxycycline.

1. Does it affect normal ("good") bacteria in our intestines?

2. Could it increase or decrease the bacteria that live on our skin, or cause bacterial resistance to doxycycline (for example staph)?

3. Will DoxyPEP increase doxycycline resistance in bacteria that cause STIs?

• Although doxycycline has been used for decades, there is no known resistance to doxycycline in chlamydia or syphilis.
• About 25% of gonorrhea in the U.S. is already resistant to doxycycline; DoxyPEP may not work against these strains. The DoxyPEP study and other studies will help understand whether using DoxyPEP changes resistance in gonorrhea.