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

Doxycycline Dosing for Post-Exposure Prophylaxis (PEP)

The recommended dosing for doxycycline PEP is a single 200 mg dose taken as soon as possible after sexual exposure but no later than 72 hours, with a maximum of 200 mg per 24-hour period. 1, 2

Target Population and Indications

• Primarily recommended for:

  • Men who have sex with men (MSM)
  • Transgender women
  • Individuals with a history of bacterial STI (syphilis, chlamydia, or gonorrhea) in the past 12 months 1, 2

• Not formally recommended for other populations due to insufficient evidence 2

Administration Guidelines

• 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 doses from dairy products, antacids, and supplements containing calcium, iron, magnesium, or sodium bicarbonate by at least 2 hours 1, 2

Efficacy

Doxycycline PEP has demonstrated significant reductions in bacterial STIs:

• Chlamydia: 70-88% reduction
• Syphilis: 73-87% reduction
• Gonorrhea: Less consistent effects, but still beneficial 2, 3

The DoxyPEP trial showed that doxycycline PEP reduced the combined incidence of gonorrhea, chlamydia, and syphilis by approximately two-thirds compared to standard care 3.

Prescription and Follow-up

1. Initial prescription:

   • Provide enough doses based on anticipated sexual activity until next follow-up visit 1
   • Assess individual behavioral patterns through shared decision-making

2. Follow-up visits (every 3-6 months):

   • Screen for STIs at anatomic sites of exposure
   • Assess for side effects
   • Re-evaluate continued need for doxy PEP
   • Provide risk reduction counseling and condoms 1, 2

Potential Side Effects and Concerns

• Common side effects:

  • Photosensitivity
  • Esophagitis and esophageal discomfort
  • Gastrointestinal intolerance (nausea, vomiting, diarrhea) 1, 2

• Antimicrobial resistance concerns:

  • Development of resistance is a significant concern with widespread use
  • Decision to use doxycycline PEP should balance short-term benefits against this risk 2
  • Monitoring for tetracycline-resistant gonorrhea is important 3, 4

Special Considerations

• Not recommended during pregnancy due to potential risks including dental staining of fetal primary teeth and possible depressed fetal bone growth 2
• May reduce effectiveness of oral contraceptives 2
• No clinically relevant interactions with gender-affirming hormonal therapy 1

Prescription Strategy

Recent evidence suggests that targeting doxycycline PEP to individuals with a history of STIs, particularly those with concurrent or repeated STIs, may be the most efficient approach to maximize impact while minimizing antibiotic use 5.

Long-term surveillance data shows sustained effectiveness of doxycycline PEP over 96 weeks, particularly for chlamydia and syphilis, with smaller effects for gonorrhea 4.