What is the recommended dosing of doxycycline (DOXY) for Post-Exposure Prophylaxis (PEP)?

Doxycycline Dosing for Post-Exposure Prophylaxis (PEP)

For post-exposure prophylaxis (PEP) of sexually transmitted infections, the recommended dose is 200 mg of doxycycline taken as a single dose within 72 hours after sexual exposure, with a maximum of 200 mg per 24-hour period. 1, 2

Eligibility and Indications

• Currently recommended for:

  • Gay, bisexual, and other men who have sex with men (MSM)
  • Transgender women
  • Who have had at least one bacterial STI (syphilis, chlamydia, or gonorrhea) diagnosed in the past 12 months 1, 2

• Not currently recommended for:

  • Cisgender women
  • Cisgender heterosexual men
  • Transgender men
  • Other queer and nonbinary persons 1, 2

Administration Guidelines

• Timing: Take 200 mg doxycycline as soon as possible after sexual exposure, but within 72 hours 1
• Frequency: Do not exceed 200 mg per 24-hour period 1
• Administration: Take with food or milk and a full glass of water 2, 3
• Position: Remain upright for at least 1 hour after taking to prevent esophageal irritation 1, 2
• Prescription quantity: Should account for enough doses based on the person's anticipated sexual activity until their next visit 1

Drug Interactions and Precautions

• Separate doxycycline by at least 2 hours from:
  • Dairy products
  • Antacids
  • Supplements containing calcium, iron, magnesium, or sodium bicarbonate 1, 2
• No clinically relevant interactions between doxycycline and gender-affirming hormonal therapy are likely 1

Monitoring and Follow-up

• Ongoing need for doxy PEP should be assessed every 3-6 months 1, 2
• Regular STI screening is recommended:
  • Nucleic acid amplification test for gonorrhea and chlamydia at anatomic sites of exposure
  • Serologic testing for syphilis
  • HIV testing for those not known to be HIV-positive 1, 2

Efficacy

• Doxy PEP has been shown to reduce:
  • Syphilis infections by >70%
  • Chlamydia infections by >70%
  • Gonococcal infections by approximately 50% 2, 4

Important Considerations

• Doxy PEP should be implemented as part of a comprehensive sexual health approach, including risk reduction counseling, regular STI screening, and appropriate vaccinations 1, 2
• Patients should be counseled about potential side effects, including photosensitivity, esophagitis, gastrointestinal intolerance, and concerns about antimicrobial resistance 1, 2
• For plague post-exposure prophylaxis (different indication), the recommended dose is 100 mg twice daily for 9 days, but this is not the focus of the current question 1

Pitfalls to Avoid

• Do not exceed 200 mg per 24-hour period for STI PEP 1
• Do not lie down for at least 1 hour after taking doxycycline to prevent esophagitis 1, 2
• Do not use doxy PEP as a replacement for other STI prevention strategies 2
• Do not prescribe without discussing potential side effects and antimicrobial resistance concerns 1

Doxycycline PEP represents an important addition to STI prevention strategies for high-risk populations, with strong evidence supporting its efficacy in reducing bacterial STIs when used appropriately.