TOPLINE:

Postexposure prophylaxis with doxycycline (DoxyPEP) was associated with a substantial decline in the incidence ofsexually transmitted infections (STIs) including Chlamydia trachomatis and Neisseria gonorrhoeae infections and syphilis among high-risk participants on preexposure prophylaxis (PrEP) for HIV infection.

METHODOLOGY:

• Researchers conducted a prospective study in Spain to evaluate the effect of DoxyPEP plus HIV PrEP vs HIV PrEP alone on the incidence of C trachomatis infection, N gonorrhoeae infection, and syphilis.
• They analyzed 197 participants on PrEP for HIV (mean age, 38.9 years), including men who have sex with men (n = 194) and transgender women (n = 3).
• All participants were administered 200 mg of doxycycline within 72 hours after any condomless sexual contact, with a maximum of one dose every 24 hours, and were followed up for a mean of 14 months.
• The primary endpoint was the incidence of C trachomatis infection, N gonorrhoeae infection, or syphilis. Secondary endpoints included tetracycline and cephalosporin resistance of N gonorrhoeae, acceptability, adherence, and safety.
• Good adherence was defined as taking DoxyPEP always or almost always within 72 hours after any condomless sexual contact.

TAKEAWAY:

• Overall, incident rates of C trachomatis infection (hazard ratio [HR], 0.24; P < .0001), syphilis (HR, 0.14; P = .0001), and gonorrhea (HR, 0.70; P = .1) decreased after starting DoxyPEP.
• Among participants who tested positive for N gonorrhoeae infection, tetracycline resistance was observed in 46.3% of those not on DoxyPEP and 42.7% of those on DoxyPEP; no cephalosporin resistance was detected.
• All participants accepted DoxyPEP treatment, and 92.9% demonstrated good adherence during follow-up.
• No serious adverse events were reported during follow-up.

IN PRACTICE:

“This real-world cohort study among HIV PrEP users demonstrates that DoxyPEP was associated with significant reduction in CT[C trachomatis]and SPL [syphilis] incidence over more than 1 year of follow-up, which could contribute to decreased transmission at the population level,” the authors wrote.

SOURCE:

This study was led by Rosario Palacios, Hospital Virgen de la Victoria, Málaga, Spain. It was published online on November 04, 2025, in the Journal of Antimicrobial Chemotherapy.

LIMITATIONS:

As it was a single-center study in a Spanish region with a high STI rate and included only men who have sex with men and transgender women on PrEP, the findings may not be generalizable.

DISCLOSURES:

This study received no financial support. The authors declared having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.