Doxycycline PEP Dosage and Instructions for STI Prevention
For STI prevention, doxycycline PEP should be taken as a single 200 mg dose within 72 hours after sexual contact, not exceeding 200 mg per 24-hour period. 1
Recommended Dosage
- Single dose of 200 mg doxycycline
- Take as soon as possible after sexual contact
- Must be taken within 72 hours of exposure
- Maximum of 200 mg per 24-hour period
Administration Instructions
- Take with a full stomach and a full glass of liquid
- Avoid lying down for at least 1 hour after taking to prevent esophagitis
- Separate doxycycline dose by at least 2 hours from:
- Dairy products
- Antacids
- Supplements containing calcium, iron, magnesium, or sodium bicarbonate
Eligible Population
The CDC specifically recommends doxycycline PEP for:
- Men who have sex with men (MSM)
- Transgender women (TGW)
- Who have had a bacterial STI (syphilis, chlamydia, or gonorrhea) diagnosed in the past 12 months 1, 2
Follow-up Recommendations
- STI screening at anatomic sites of exposure every 3-6 months
- HIV screening according to current CDC guidelines
- Assessment of side effects from doxycycline
- Re-evaluation of continued need for doxy PEP every 3-6 months
- Risk reduction counseling and provision of condoms 1
Potential Side Effects
- Photosensitivity
- Esophagitis and esophageal discomfort
- Gastrointestinal intolerance (nausea, vomiting, diarrhea)
- Potential for antimicrobial resistance development 1, 2
Effectiveness
Recent studies have demonstrated significant reductions in bacterial STI acquisition with doxycycline PEP:
- Reduces transmission of syphilis, gonorrhea, and chlamydia by approximately two-thirds in high-risk populations 3
- Most effective against chlamydia and syphilis, with less consistent effectiveness against gonorrhea 4, 5
Important Considerations
- Not recommended during pregnancy due to potential risks including dental staining of fetal primary teeth and possible depressed fetal bone growth 1
- May reduce effectiveness of oral contraceptives 2
- Should be prescribed as part of a comprehensive sexual health approach including regular STI screening and risk reduction counseling
- Antimicrobial resistance is a significant concern with widespread use 1, 2
This approach represents a novel STI prevention strategy that has shown significant benefit in reducing incident bacterial STIs in specific high-risk populations, though ongoing monitoring for antimicrobial resistance is essential.