Efficacy and implementation considerations for a peer-led motivational interviewing intervention to promote uptake of drug checking services and safer drug use behaviors to reduce overdose - We will conduct a hybrid type 1 study to evaluate efficacy and preliminary implementation considerations for a novel intervention to promote uptake of drug checking services (DCS) and safer drug use behaviors among people who use drugs (PWUD) to reduce incidence of overdose (OD) in San Diego County. Along with ~50 other syringe services programs (SSPs) in the US, a local SSP recently began CheckSD, a DCS using test strips (TS) and Fourier Transform Infrared Spectrometry (FTIR) that allows people to submit drug samples with non-nominal identifiers and obtain personalized results. While CheckSD and most existing DCS with FTIR offer some counseling about DCS results, no theory-based interventions to increase DCS uptake and promote post-DCS adoption of safer drug use behaviors have been rigorously evaluated. We drew from the Social Ecological Model and Social Cognitive Theory (SCT) to develop and pilot MI-CHANCE (Motivational Interviewing for Community-based Harm reduction And drug-Checking Empowerment), a brief, bilingual, peer-led MI intervention. We culturally-tailored MI-CHANCE because Latinx PWUD are less likely to access harm reduction services, contributing to racial/ethnic disparities in OD rates. Our Aims are: Aim 1. To test the efficacy of MI-CHANCE on rates of combined fatal and non-fatal OD over 30 months and examine SCT-informed mediators and moderators of intervention effects (i.e., knowledge, outcome expectancies, self-efficacy). Aim 2. To conduct an inward-looking implementation evaluation to examine MI-CHANCE acceptability, feasibility and experiences among i) trial participants and ii) SSP staff in San Diego County; iii) collect data on implementation costs of MI-CHANCE and CheckSD to inform adoption by SSPs and policy-makers. Aim 3. To conduct an outward-looking exploration of MI-CHANCE's scalability among SSP staff at 20 other U.S. locations, purposively sampled to represent nascent and established DCS. To meet Aim 1, we will recruit 588 PWUD who have not yet used CheckSD into a two-arm RCT (N=294 per group). Both arms will have access to CheckSD's standard of care (SOC) already available at SSP sites (i.e., FTIR, and overdose education and naloxone distribution). PWUD randomized to receive MI-CHANCE will receive it from peer counselors trained in MI to encourage CheckSD uptake and safer drug use behaviors. Those in the attention-control SOC arm will receive COVID-19 education. All will undergo semi-annual follow-up for 30 months. Aims 2-3 will be guided by the revised RE-AIM/PRISM implementation science framework. This will be the first trial to rigorously evaluate efficacy and preliminary implementation of an intervention to optimize DCS uptake and behavioral outcomes for reducing OD. Despite the high promise of DCS, it is an innovation for which real world implementation is ahead of—but could be strengthened by—empirical research on behavioral intervention and implementation supports. If MI-CHANCE is efficacious, it could be rapidly deployed at harm reduction programs across the country to reduce OD deaths and disparities due to changes in the drug supply. This study is part of the NIH’s Helping to End Addiction Long-term (HEAL) initiative to speed scientific solutions to the national opioid public health crisis. The NIH HEAL Initiative bolsters research across NIH to improve treatment for opioid misuse and addiction.