What is the recommended dosage and duration for doxycycline (Vibramycin) when used for post-exposure prophylaxis (PEP)?

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Doxycycline Post-Exposure Prophylaxis (DoxyPEP) Prescription

Take doxycycline 200 mg by mouth as a single dose within 72 hours after condomless oral, vaginal, or anal sex, with a maximum of 200 mg per 24-hour period. 1, 2

Dosing Instructions

The prescription should provide enough doses based on anticipated sexual activity until the next follow-up visit (typically 3-6 months). 1, 2

  • Take 200 mg (two 100 mg tablets or one 200 mg tablet) as soon as possible after sexual exposure, but no later than 72 hours 1, 2
  • Do not exceed 200 mg in any 24-hour period 1
  • Take on a full stomach with a full glass of water 1, 2
  • Remain upright (do not lie down) for at least 1 hour after taking to prevent esophagitis 1, 2

Drug Interactions and Timing

  • Separate doxycycline by at least 2 hours from dairy products, antacids, and supplements containing calcium, iron, magnesium, or sodium bicarbonate 1, 2
  • No clinically significant interactions with gender-affirming hormonal therapy 1
  • Review all medications including over-the-counter products for potential interactions 1

Important Counseling Points

Photosensitivity is a common side effect—avoid direct sunlight and UV radiation during treatment. 2

  • Other common side effects include gastrointestinal intolerance (nausea, vomiting, diarrhea) and esophageal discomfort 1
  • Chronic alcohol consumption may reduce doxycycline serum levels and decrease efficacy 2
  • This medication is specifically for STI prevention after sexual exposure—do not use for other purposes 1

Follow-Up Schedule

  • Screen for gonorrhea, chlamydia, and syphilis at baseline and every 3-6 months 1
  • Reassess continued need for doxyPEP every 3-6 months 1, 2
  • Monitor for side effects at each follow-up visit 1

Sample Prescription Sig

"Take 200 mg by mouth within 72 hours after condomless sex. Maximum one dose per 24 hours. Take with full glass of water on full stomach. Stay upright for 1 hour after taking. Avoid sun exposure." 1, 2

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Guideline

Doxycycline Prophylaxis Guidelines

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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