Photo Credit: iStock.com/Eskymaks

New research showed higher rates of STIs and STI recurrence in MSM using PrEP who reported engaging in sexualized drug use, or “chemsex.”

An observational cohort study of men who have sex with men (MSM) using HIV pre-exposure prophylaxis (PrEP) identified a high incidence of bacterial sexually transmitted infections (STIs), with a disproportionate impact among those who reported sexualized drug use, or “chemsex.”

The researchers reported the findings in Wiener klinische Wochenschrift.

As Birgit Willinger, MD, and colleagues noted, “MSM are the primary target group for PrEP services as, compared to the general population, they are more likely to engage in condomless anal intercourse with casual partners as well as in sexualized drug use (chemsex).”

Further, they noted that chemsex has increased in prevalence in many Western countries and has been correlated with sex practices prone to HIV transmission, such as condomless anal intercourse. Chemsex is also associated with a higher STI prevalence, according to Dr. Willinger and colleagues.

Reinfections Account for Nearly 70% of STIs

The prospective study enrolled 360 people (median age, 31.2), all but one of whom identified as MSM (n=359); the other participant (n=1) identified as a transgender woman. All participants were using or had started PrEP at an HIV and STI outpatient clinic. They underwent quarterly STI testing and completed questionnaires about sexual behaviors. The follow-up period included 379 person-years.

The researchers identified 276 STIs in 154 people. In total, 23% of infections were symptomatic. Patients with one or more reinfection (18%; 65/360) accounted for 68% (187/276) of all STIs.

Per 100-person years, incident rates were 29.9 for gonorrhea, 22.7 for chlamydia, and 9.8 for syphilis. Nearly all (95%) gonorrhea cases and most (81%) cases of chlamydia were extragenital infections. A single HIV infection occurred in a 20-year-old man with inconsistent PrEP use. No hepatitis C virus infections were detected.

Chemsex Linked to Higher Rates of STIs

Chemsex, which was reported by 44% of participants, was significantly linked with higher rates of gonorrhea (38% vs 21%; P<0.001) and syphilis (17% vs 5%; P<0.001), but not chlamydia (26% vs 19%).

“The impact of chemsex on STI risk emerged as a critical finding in our research,” the authors wrote. “Participants engaging in chemsex not only exhibited higher rates of STIs but also were more likely to experience reinfections.”

Together, the findings underscore “the importance of harm reduction strategies” in STI prevention for PrEP users, Dr. Willinger and colleagues noted.