5PSQ-047 Dynamics of HIV pre-exposure prophylaxis use and evaluation of its impact in the incidence of sexually transmitted diseases

<h3>Background and Importance</h3> HIV pre-exposure prophylaxis (PrEP) effectively reduces the risk of HIV transmission. However, its use has been associated with changes in sexual practices, which may influence the risk of acquiring other sexually transmitted diseases (STDs). This study investigates PrEP adherence and explores trends in STD acquisition during PrEP treatment. <h3>Aim and Objectives</h3> To evaluate PrEP adherence among users and describe the patterns of STD acquisition during treatment. <h3>Material and Methods</h3> This was a multicentre, observational, retrospective cohort study of patients who received PrEP for more than 30 days between June 2023 and June 2024. Data were collected from electronic prescription and medical records systems. Qualitative variables: sex, comorbidities, partner’s HIV status, chemsex use, condom use, treatment interruptions and their causes, STD and/or HIV acquired during treatment, microorganisms and treatment. Quantitative variables included age, number of sexual partners, duration of PrEP treatment and adherence (measured using the dispensing registry). Statistical analysis was performed using R Commander software. Data were obtained from electronic prescription and medical records applications. <h3>Results</h3> 117 patients included, 99% men, with a median age of 36 years (IQR 30–45). Median of 20 sexual partners per year (IQR 12.7–36); irregular condom use in 54.3%; consistent condom use in 23.2%; 22.5% reported no condom use. Chemsex was practiced by 23.3%. During oral sex, 95.6% never used condoms. Risky sexual relationships were frequent for 15.5% of patients and 10.3% had taken post-exposure prophylaxis previously. Median treatment duration of 18.6 months (IQR 8.8–28.7); adherence was 81.8%. No treatment-associated adverse effects were observed. Treatment was interrupted by 49.3%, with 21.3% switching to on-demand use. 79.3% acquired an STD during treatment, with Neisseria gonorrhoeae (43.4%) and Chlamydia trachomatis (29.1%) being most common. A small proportion of Mycoplasma genitalium cases showed resistance to azithromycin (38.8%) and moxifloxacin (22.2%). Only one patient contracted HIV while on PrEP. <h3>Conclusion and Relevance</h3> PrEP is an essential tool for HIV prevention, and adherence among patients in this study was high. However, a significant proportion of users acquired STDs during treatment, suggesting the need for ongoing STD screening and education. While this study highlights trends in STD acquisition, it does not establish causality between PrEP use and increased STD risk. Multidisciplinary efforts are vital to optimising PrEP’s protective benefits and mitigating the risks of other infections. <h3>References and/or Acknowledgements</h3> <h3>Conflict of Interest</h3> No conflict of interest