Development of a Line of Care for the Health of People Who Engage in Chemsex: Protocol for a Multimethod Study

Background Chemsex, defined as the intentional use of psychoactive substances to enhance sexual experiences, is associated with increased risk of sexually transmitted infections (STIs), mental health harms, and disruptions in continuity of care, particularly among men who have sex with men. In Brazil, health services lack an integrated, stigma-sensitive care pathway (CP) for prevention, clinical management, and harm reduction. Embedding a CP within the Health Care Network (HCN) is essential to organize access, continuity, and quality of care. Objective This study aims to develop an evidence-informed CP for people who engage in chemsex, grounded in the needs of users, managers, and health professionals within the HCN, and supported by educational tools and implementation strategies. Methods This sequential multimethod study is guided by the Knowledge-to-Action framework. Phase 1 (predevelopment) focuses on establishing partnerships and mapping the local context. Phase 2 (Knowledge Creation) includes (1) cross-sectional surveys with adults from the general population (target n≈1600) to estimate chemsex prevalence and associated factors, and with managers (n≈54) and health professionals (n≈135) to assess knowledge, attitudes, practices, barriers, and stigma; (2) a scoping review following established methodological guidelines; and (3) triangulation and concept mapping to integrate quantitative and qualitative findings. Data will be collected via REDCap (Research Electronic Data Capture), online and in person, during testing events. Quantitative analyses will involve descriptive statistics and regression models. Interviews and focus groups will undergo thematic analysis supported by Nvivo software. Educational products will be developed and evaluated for appearance, content, and usability by experts using a content validity index ≥0.78 as a cutoff. Phase 3 (Action Cycle) includes adapting knowledge to the local context, co-designing and validating the CP with stakeholders, piloting implementation in priority municipalities, and establishing monitoring processes. Process indicators (eg, number of trained professionals, educational activities, rapid tests performed, and app engagement) and outcome indicators (eg, STI testing and linkage to care, service use across the HCN) will be monitored through official information systems. Results Ethical approval was obtained in April 2025. Recruitment and data collection began in June 2025 through online and in-person strategies. By December 2025, 3061 individuals had been screened online, and 1723 participants had undergone rapid testing for STIs. Data collection is expected to conclude by June 2026, followed by data cleaning and preliminary analyses between April and June 2026, inferential and qualitative analyses between July and September 2026, and CP development and validation between October and December 2026. Conclusions This protocol will generate a CP tailored to chemsex and validated educational resources to support harm reduction, mental health, and STI prevention within the HCN. Findings are expected to inform inclusive policies, reduce stigma, and strengthen care coordination within Brazil’s Unified Health System. International Registered Report Identifier (IRRID) DERR1-10.2196/84068