200 mg of doxycycline (2 pills, 100 mg each) should be taken orally ideally within 24 hours but no later than 72 hours after condomless oral, anal, or vaginal intercourse.
Doxy-PEP can be taken as often as every day, but should not exceed more than 200 mg within a 24 hour period.
Efficacy against other bacterial STIs is not known, and doxy-PEP does not prevent HIV, MPOX (monkeypox) or other viral infections like HPV and HSV
Side effects may include heightened sun sensitivity, upset stomach, and heartburn. We recommend using sunscreen for 24-48 hours following your dose. Taking doxycycline with food can also help with nausea.
Metals like zinc, magnesium, iron and calcium can reduce the effectiveness of doxycycline. Avoid these supplements along with antacids, heartburn medications and dairy products for 2 hours before and after taking doxy-PEP.
There is not strong evidence at this time showing that taking doxycycline before STI exposure prevents infections