People Using Illicitly Sourced Fentanyl Face Worse Outcomes Than Medically Sourced Users

FRIDAY, Sept. 4, 2026 (HealthDay News) — Illicit-source fentanyl exposure is linked to a significantly higher risk of opioid-related harmful outcomes than medical-source exposure, according to a study published online Aug. 14 in eClinicalMedicine.

Seungyeon Lee, from The Ohio State University in Columbus, and colleagues used Epic Cosmos electronic health records to characterize individual-level illicit fentanyl exposure. Longitudinal patterns and risks for opioid-related harmful outcomes were compared for 85,535 individuals in the medical-source cohort (MSC) and 210,193 in the illicit-source cohort (ISC).

The researchers found that from 2015 to 2023, the prevalence of nonfatal opioid overdose was consistently higher in the ISC (18.6 percent) versus the MSC (4.3 percent). The ISC also had higher prevalence of opioid dependence and abuse, with steeper year-over-year increases versus the MSC until 2020. While remaining higher than the MSC, after 2020, prevalence of opioid dependence and abuse in the ISC declined, particularly for dependence. A significantly elevated risk for 30-day opioid-related harmful outcomes was associated with illicit-source fentanyl initiation (adjusted hazard ratios, 2.99 for overdose; 1.96 for abuse; 3.05 for dependence) compared with medical-source initiation. 

“Inferring or characterizing individual-level illicit fentanyl exposure poses significant challenges because illicit use often occurs outside the clinical setting and therefore is not directly observed in clinical data, so it’s difficult to measure the scale and impact,” Lee said in a statement. 

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