Norfentanyl detection after negative confirmatory testing following heavy illicit fentanyl exposure: A two‐patient case series
Daisy Valdivieso, Maryam SoltaniAbstract
Background and Objectives
Prolonged fentanyl detection may complicate urine drug testing (UDT). We describe norfentanyl detection after negative confirmatory testing.
Methods
Two patients ( N = 2) entering residential treatment after heavy illicitly manufactured fentanyl exposure underwent clinically indicated serial UDT with confirmatory LC‐MS/MS.
Results
Both had negative confirmatory results followed by subsequent low‐level urinary norfentanyl detection. Recurrent exposure could not be excluded.
Discussion
These findings demonstrate diagnostic uncertainty rather than a defined pharmacokinetic mechanism.
Conclusions and Scientific Significance
Low‐level norfentanyl after negative confirmatory testing should prompt longitudinal assessment rather than automatic attribution to recurrent use or prolonged detection.