ABSTRACT Introduction The illicit drug supply constantly fluctuates, with new adulterants and unexpected mixtures creating uncertainty. Point‐of‐care drug‐checking services are vital in reducing overdose risk and other harms by providing real‐time analysis, harm reduction education and links to care. This study aimed to characterise the local drug supply using Fourier transform infrared (FTIR) spectroscopy, complemented by Liquid Chromatography‐Quadrupole time‐of‐flight Mass Spectrometry (LC‐QToF‐MS) for additional context, from drug residues collected through a drug‐checking program within a Rhode Island harm reduction site. Methods From January to May 2023, 100 samples were analysed using FTIR and sent for additional qualitative and semi‐quantitative testing via LC‐QToF‐MS. Substances detected by both methods were summarised by prevalence, mixture composition and alignment with self‐reported drug categories. Results Fentanyl (53%) and cocaine (48%) were the most prevalent substances detected by FTIR, followed by xylazine (10%) and methamphetamine (8%). Cross‐category analysis revealed cocaine in 36% of opioid‐reported samples and fentanyl in 3% of self‐reported cocaine samples, underscoring the mixed nature of the supply. We found the local fentanyl supply ( n = 57) showed high variability, with 15 additional components detected by FTIR, including xylazine (19.3%). Discussion and Conclusions These findings provide a snapshot of the unpredictable and highly mixed nature of the Rhode Island drug supply defined by stimulant‐opioid overlaps, xylazine adulteration and the presence of cocaine across drug categories. By pairing real‐time FTIR with laboratory‐based analysis, we provided actionable information back to service users while also uncovering deeper patterns in local drug trends.
Ujeneza et al. (2025) studied this question.