Norfentanyl detection after negative confirmatory testing following heavy illicit fentanyl exposure: A two-patient case series.

Authors

Daisy Valdivieso, Maryam Soltani

Published in

The American journal on addictions. Oct 19, 2026. Epub Oct 19, 2026.

Abstract

Prolonged fentanyl detection may complicate urine drug testing (UDT). We describe norfentanyl detection after negative confirmatory testing.
Two patients (N = 2) entering residential treatment after heavy illicitly manufactured fentanyl exposure underwent clinically indicated serial UDT with confirmatory LC-MS/MS.
Both had negative confirmatory results followed by subsequent low-level urinary norfentanyl detection. Recurrent exposure could not be excluded.
These findings demonstrate diagnostic uncertainty rather than a defined pharmacokinetic mechanism.
Low-level norfentanyl after negative confirmatory testing should prompt longitudinal assessment rather than automatic attribution to recurrent use or prolonged detection.

PMID:
42895990
Bibliographic data and abstract were imported from PubMed on 20 Oct 2026.

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