Abstract
BACKGROUND: Aim is to evaluate the changes in antimicrobial consumption of ceftriaxone, benzylpenicillin and doxycycline for the treatment of bacterial sexually transmitted infections (bSTIs), after the prescription of doxycycline post-exposure prophylaxis (DoxyPEP) among men who have sex with men (MSM). METHODS: Retrospective study of MSM in care for HIV or HIV pre-exposure prophylaxis (PrEP) at the Infectious Diseases Unit of San Raffaele Hospital, Milan, Italy, who received DoxyPEP counselling and prescription from August 2022 (first DoxyPEP prescription, baseline) to July 2024 (data lock). DoxyPEP was offered to people with ≥1 STI or reporting condomless sex with ≥1 partner. DoxyPEP with doxycycline 200mg within 72 h of potential exposure was suggested for intensive sexual activity (>5 partners). All individuals with ≥1 follow-up visit after baseline and ≥1 before were included. DoxyPEP use was self- reported during routine visits. Individuals were tested for bSTIs (syphilis, Tp; chlamydia, Ct; gonorrhea, Ng) every 3–6 months according to local practice. Adjusted % change (and 95% confidence interval, CI) in incidence rate (IR) of STIs before and after DoxyPEP prescription were estimated using a pre-post within-person analysis by Poisson mixed-effects model. Use of DoxyPEP and ceftriaxone, benzylpenicillin, doxycycline for bSTIs treatment was quantified as days of therapy (DOT) per 1000 person-days (1000-PD). The observed DOTs after DoxyPEP prescription were increased with %changes derived from regressions to obtain the expected DOTs in absence of DoxyPEP. RESULTS: Overall, 754 MSM were prescribed DoxyPEP; during follow-up 222 (29.4%) reported using DoxyPEP. Median follow-up among DoxyPEP users were 15.8 months (IQR = 12.1–19.2) and 10.8 (6.88–13.1) before and after prescription, respectively. Individuals' characteristics in Table 1. Among DoxyPEP users, 401 bSTIs (Tp 70, Ct 139, Ng 192) were detected before DoxyPEP prescription and 146 (Tp 26, Ct 32, Ng 88) after. Overall, DOT per 1000-PD was 1.26 for ceftriaxone, 0.37 for penicillin and 3.21 for doxycycline after DoxyPEP prescription; DoxyPEP DOT per 1000-PD was 7.00. Expected DOT per 1000-PD in the absence of DoxyPEP was 4.85 (95%CI = 3.82–6.41) for ceftriaxone, 1.86 (95%CI = 1.17–2.87) for penicillin, and 24.71 (95%CI = 17.18–37.36) for doxycycline. CONCLUSIONS: A significant reduction in all considered antibiotics used for the treatment of bSTIs was achieved among DoxyPEP users. [Figure: see text]