Doxycycline for Post Exposure Prophylaxis- Decreasing Syphilis and Chlamydia Infections but not Ready for Prime Time

Source: Web MD

Doxycycline may have a potential new niche, this time for STI post exposure prophylaxis. 

This recent article in Lancet Infectious Diseases reports significant reductions in chlamydia and syphilis infections in men who have sex with men on HIV PrEP when taking a 200 mg dose of doxycyline post sexual activity.

To have a population based impact, per this previous publication, doxycycline would have to 70% effective at preventing syphilis and taken by 50% of sexually active gay men for syphilis rates to decrease by 50%.

All of this is tantalizing but concerns are aplenty. Condom use continues to decrease with patients on post-exposure prophylaxis. The impact of doxycycline use on antimicrobial stewardship efforts and emergence of antibiotic resistance in chlamydia and syphilis isolates are real. Study results must be replicated for greater validity.

Doxycycline as post exposure prophylaxis for the prevention of sexually transmitted infections  is not yet ready for prime time.