Doxycycline postexposure prophylaxis (doxyPEP) in a patient with antiphospholipid syndrome receiving warfarin: balancing STI prevention and anticoagulation safety

Doxycycline postexposure prophylaxis (doxyPEP) is an emerging strategy in the prevention of syphilis and chlamydia in selected high-risk groups.1 However, its introduction into routine sexual health practice may create prescribing dilemmas in patients receiving warfarin. We describe a 57-year-old man who has sex with men who presented requesting doxyPEP following a recent rectal Lymphogranuloma venereum chlamydia infection, specific, aggressive form of chlamydia infection associated with severe rectal inflammation (proctitis). His medical history included high-risk antiphospholipid syndrome diagnosed after a myocardial infarction secondary to arterial thrombosis and treated with warfarin (target international normalised ratio (INR) 2–3). His medication list also included aspirin, pre-exposure prophylaxis (emtricitabine/tenofovir disoproxil), insulin, losartan, Nustendi, esomeprazole, Fostair and sildenafil.

Although he met the criteria for doxyPEP, the concurrent use of doxycycline and warfarin was identified as a clinically important interaction with the potential to potentiate anticoagulation and increase bleeding risk.2 Because doxyPEP is taken…

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