Decreasing fentanyl concentrations in urinalysis results for methadone treatment admissions: Evidence of changing fentanyl exposure in street drugs.

BACKGROUND

Recent declines in opioid-related overdose fatalities (OROF) in Chicago and nationally in the U.S. have prompted questions about whether changes in fentanyl exposure may be occurring in the illicit opioid supply.

OBJECTIVE

This study examined temporal trends in fentanyl exposure among individuals entering opioid treatment, using admission urinalysis as a biological indicator of recent opioid exposure.

METHODS

We conducted a secondary analysis of clinical admission data collected between 2023 and 2025 from a community-based opioid treatment program (OTP) on Chicago's West Side (N = 339). Multivariable ordinary least squares regression models were used to examine changes in log-transformed urine concentrations of fentanyl, norfentanyl, and morphine across admission years, adjusting for sociodemographic and clinical characteristics. Concentration analyses were restricted to participants with confirmed positive tests.

RESULTS

Relative to 2023, fentanyl concentrations were significantly lower in 2024 (b = -0.77, p < 0.001) and 2025 (b = -1.29, p < 0.001), corresponding to approximately 54% and 72% reductions, respectively. Norfentanyl concentrations also declined over time, while morphine concentrations remained stable. Participant characteristics and the prevalence of opioid detection at admission were largely stable across years.

CONCLUSIONS

Declining concentrations of fentanyl and norfentanyl, alongside stable morphine levels, suggest reduced fentanyl exposure among treatment-seeking individuals over the study period. While urinalysis provides an indirect indicator and cannot establish causality, these findings are consistent with broader reports of declining fentanyl-related overdose mortality and highlight the potential value of treatment-entry toxicology data as a sentinel indicator of changes in illicit opioid markets.