Doxy-PEP: Evidence, Limits and Use

Overview

Doxy-PEP is an event-driven 200 mg dose taken as soon as possible after condomless sex, ideally within 24 hours and no later than 72 hours. Across the studied populations, it sharply reduces syphilis and chlamydia and provides a smaller, more setting-dependent reduction in gonorrhoea. The series explains how timing, mucosal exposure, pathogen susceptibility, population fit and follow-up shape those results. It also shows why current recommendations are targeted and conditional: doxy-PEP complements testing and treatment, while adverse effects, antimicrobial resistance, equity and uncertain transfer to other populations require shared decisions and monitoring.

Learning outcomes

Doxy-PEP shows the strongest, high-certainty pooled reductions for syphilis and chlamydia in the studied populations.
Gonorrhoea benefit is meaningful but smaller, moderately certain and more dependent on local tetracycline resistance.
A 200 mg dose is studied after sex, ideally within 24 hours and no later than 72 hours; daily PrEP is not established.
Targeting, testing, shared decisions and AMR surveillance help align antibiotic exposure with changing benefit and harm.

Keywords

Doxy-PEPsyphilischlamydiagonorrhoeatimingsusceptibilityresistanceadherencesurveillancetesting

Chapters

Doxy-PEP: One Dose, Three STI Results

Why pathogen and context shape the result

10 min · Why pathogen and context shape the result

10 min

Doxy-PEP: The 72-Hour Window

How timing links exposure to prevention

7 min · How timing links exposure to prevention

7 min

Doxy-PEP Trial Results by STI

How pooled estimates and study differences change the picture

12 min · How pooled estimates and study differences change the picture

12 min

Doxy-PEP: Four Gates to Protection

A conditional model for timing, exposure and context

10 min · A conditional model for timing, exposure and context

10 min

Doxy-PEP and Gonorrhoea Resistance

Why local susceptibility and surveillance matter

11 min · Why local susceptibility and surveillance matter

11 min

Doxy-PEP Evidence Across Populations

What the Kenyan trial can—and cannot—show

9 min · What the Kenyan trial can—and cannot—show

9 min

Doxy-PEP: Targeting and Stewardship

How follow-up keeps benefit and harm in balance

12 min · How follow-up keeps benefit and harm in balance

12 min

What Doxy-PEP Can and Cannot Promise

A conditional guide to benefit, limits and monitoring

11 min · A conditional guide to benefit, limits and monitoring

11 min

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FAQ

How effective is doxy-PEP against syphilis, chlamydia and gonorrhoea?

In pooled randomized evidence, doxy-PEP reduced relative risk by about 80% for syphilis, 85% for chlamydia and 48% for gonorrhoea under the studied conditions. Evidence certainty was high for syphilis and chlamydia and moderate for gonorrhoea.

Why does the same doxy-PEP dose produce different results?

The same event-driven dose meets pathogens with different susceptibility profiles in different mucosal, population and service contexts. Timing and useful drug exposure matter, while gonorrhoea benefit is especially sensitive to local tetracycline resistance.

Who does current doxy-PEP guidance focus on?

Current WHO and CDC guidance focuses on men who have sex with men and transgender women with elevated or recent STI risk, although the eligibility and decision process differ. Evidence for cisgender women and other populations remains limited rather than proving doxy-PEP cannot work there.

What does responsible doxy-PEP use require?

Responsible use pairs event-driven dosing with shared decision-making, testing, treatment, follow-up, side-effect review and antimicrobial-resistance surveillance. It targets likely benefit rather than universal use and reassesses need as risk, tolerance and local evidence change.