Doxycycline PEP for Continuous Sexual Activity
For continuous sexual activity over a period like one week, doxycycline PEP should be taken as a single 200mg dose after each sexual encounter, with a maximum of one 200mg dose per 24-hour period, taken within 72 hours of exposure. 1, 2
Doxycycline PEP Dosing Guidelines
- Standard dosing: 200mg doxycycline taken as soon as possible after condomless sex, but within 72 hours of exposure 1
- Maximum dosing: Do not exceed 200mg in a 24-hour period 1, 2
- For continuous sexual activity: Take one 200mg dose after sexual activity, maintaining the 24-hour minimum interval between doses 1
- Duration of protection: Each 200mg dose provides protection for encounters within the previous 72 hours 1
Proper Administration
- Take doxycycline with food and a full glass of water (8 oz) 3
- Remain upright for at least one hour after taking the medication to prevent esophageal irritation 3
- Avoid dairy products, antacids, and supplements containing calcium, iron, or magnesium for 2-3 hours before or after taking doxycycline 3
Doxycycline PrEP vs. PEP
While your question mentions "doxy PrEP," it's important to clarify that current guidelines primarily support doxycycline as post-exposure prophylaxis (PEP) rather than pre-exposure prophylaxis (PrEP) 1:
- Doxy PEP: Taking doxycycline after potential exposure (currently recommended)
- Doxy PrEP: Daily doxycycline regardless of sexual activity (not currently recommended in guidelines)
The Taiwan guidelines do describe an "on-demand" or "event-driven" PrEP approach for HIV prevention using TDF/FTC, but this should not be confused with doxycycline PrEP 1.
Efficacy and Population Considerations
Doxycycline PEP has demonstrated significant efficacy in specific populations:
- Reduces chlamydia infections by 70-88% 3, 4
- Reduces syphilis infections by 73-87% 3, 4
- Less consistent protection against gonorrhea due to resistance patterns 3, 4
Current CDC guidelines specifically recommend doxycycline PEP for:
- Men who have sex with men (MSM)
- Transgender women
- Particularly those with a history of bacterial STIs in the past year 1
There is insufficient evidence to recommend doxycycline PEP for cisgender women, cisgender heterosexual men, transgender men, and other gender-diverse individuals at this time 1.
Monitoring and Follow-up
- Return for STI screening every 3-6 months 1
- Assess for side effects and continued need for doxycycline PEP at each visit 1
- Monitor for common side effects: gastrointestinal issues, photosensitivity, esophageal discomfort 3
Important Cautions
- Potential for antimicrobial resistance development with prolonged use 1, 3
- Studies have shown increased tetracycline-resistant S. aureus with extended doxycycline use 1
- Doxycycline PEP should be part of a comprehensive sexual health approach including other prevention strategies 1
For continuous sexual activity over a week, the key is maintaining the maximum of 200mg per 24-hour period while ensuring each dose is taken as soon as possible after exposure, within the 72-hour window.