{
  "abstract": "Background Chemsex refers to the intentional use of psychoactive substances in sexual contexts, predominantly among MSM in order to prolong and intensify sexual experiences. Substances commonly associated with chemsex include GHB/GBL, synthetic cathinones, and crystal methamphetamine, often in combination with other drugs.Through sexual disinhibition and prolonged encounters, chemsex may amplify exposure to HIV and other sexually transmitted infections (STIs).Our study aims to evaluate the frequency of chemsex and its associated factors within Prevention ICONA Dedicated Ensemble (PrIDE), the largest nationwide Italian PrEP cohort.Methods Information on substance use, chemsex practices, and sexual behaviors was collected through anonymous self-administered questionnaires in 2025 and linked to clinical data from medical records, including demographics, history of STIs, prior post-exposure prophylaxis (PEP), sex work, and doxycycline post-exposure prophylaxis (doxy-PEP).Continuous variables are presented as medians with interquartile ranges (IQR); categorical variables as counts and percentages. Group comparisons used Wilcoxon rank-sum, chi-squared, or Fisher’s exact tests as appropriate. Multivariable logistic regression identified factors independently associated with chemsex engagement.Results Among 2,180 PrEP users included in the analysis ( table 1), 279 (13.0%) reported chemsex engagement. Prevalence was comparable across macro-regions (13.2% in northern vs 11.5% in central–southern Italy). The substances most frequently reported were mephedrone (60.6%), GHB/GBL (41.9%), and cocaine (40.5%). Ketamine use was also substantial, reported by 69 participants (24.7%), as well as crack cocaine (56; 20.1%), MDPV (56; 20.1%), and crystal methamphetamine (40; 14.3%) (table 2).In adjusted analyses, chemsex was positively associated with transgender/non-binary identity (OR 3.90; 95% CI 1.60–8.99), fisting (OR 3.30; 95% CI 2.36–4.60), group sex (OR 2.86; 95% CI 1.91–4.37), doxy-PEP use (OR 1.80; 95% CI 1.15–2.78), and prior STI diagnosis (OR 1.51; 95% CI 1.13–2.02). Condom use (OR 0.38; 95% CI 0.26–0.68) and age >50 years (OR 0.51; 95% CI 0.30–0.89) were inversely associated.Conclusions In this large Italian PrEP cohort, 13% of participants reported chemsex. The strong associations with high-risk sexual practices and prior STI history underscore the need for integrated models of care within PrEP services. Harm-reduction counseling, substance-use assessment, and strategies that can support adherence should be incorporated into routine practice.Although the number of transgender and non-binary participants was limited, the association with chemsex engagement highlights the importance of gender-affirming and structurally sensitive prevention programs.Abstract OC21 Table 1Distribution of cohort characteristics overall and by chemsex statusAbstract OC21 Table 2Prevalence of substance use among participants according to chemsex",
  "authors": [
    {
      "affiliations": [
        "Department of Infectious Diseases, Luigi Sacco University Hospital, Milan, Italy"
      ],
      "name": "C Fusetti"
    },
    {
      "affiliations": [
        "Department of Infectious Diseases, Luigi Sacco University Hospital, Milan, Italy"
      ],
      "name": "D Moschese"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases Lazzaro Spallanzani IRCCS, Rome, Italy"
      ],
      "name": "G Frate"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases Lazzaro Spallanzani IRCCS, Rome, Italy"
      ],
      "name": "G Micheli"
    },
    {
      "affiliations": [
        "Milano Checkpoint ETS, Milan, Italy"
      ],
      "name": "E Caruso"
    },
    {
      "affiliations": [
        "CeMuSS (Multidisciplinary Sexual Health Center), ASL Città di Torino, Turin, Italy"
      ],
      "name": "AM Lucchini"
    },
    {
      "affiliations": [
        "Infectious Diseases Unit, Vita Salute San Raffaele University, Milan, Italy"
      ],
      "name": "AR Raccagni"
    },
    {
      "affiliations": [
        "Clinic of Infectious Diseases and Tropical Medicine, ASST Santi Paolo e Carlo, Milan, Italy"
      ],
      "name": "C Tincati"
    },
    {
      "affiliations": [
        "Department of Infectious Diseases, Luigi Sacco University Hospital, Milan, Italy"
      ],
      "name": "S Lazzarin"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases Lazzaro Spallanzani IRCCS, Rome, Italy"
      ],
      "name": "D Farinacci"
    },
    {
      "affiliations": [
        "Milano Checkpoint ETS, Milan, Italy"
      ],
      "name": "M Cernuschi"
    },
    {
      "affiliations": [
        "Infectious Diseases Unit, Vita Salute San Raffaele University, Milan, Italy"
      ],
      "name": "S Nozza"
    },
    {
      "affiliations": [
        "National Institute for Infectious Diseases Lazzaro Spallanzani IRCCS, Rome, Italy"
      ],
      "name": "V Mazzotta"
    }
  ],
  "title": "OC21 Chemsex practices and behavioral determinants among PrEP Users in the Italian PrIDE cohort",
  "uid": "fd62f2af-333c-589a-ad83-d77bf9be6d20"
}