Delayed Norfentanyl Clearance During Pregnancy.

Wanar, Amita; Saia, Kelley; Field, Thomas A · Obstet Gynecol · 2020

case_report · Level V

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Abstract

We report a case of delayed norfentanyl clearance in a 33-year-old pregnant woman. Norfentanyl is the major metabolite of fentanyl. A multigravid woman with opioid use disorder presented at 7 weeks of gestation for treatment. Despite opioid abstinence, her urine was positive for norfentanyl on 10 distinct gas chromatography-mass spectrometry urine screens. The results demonstrated a steady decrease of norfentanyl over the course of 70 days after her last fentanyl usage, far exceeding expected rates of fentanyl clearance. This case highlights the importance of acknowledging pregnancy, genetic, or medication-induced changes to fentanyl pharmacokinetics when interpreting urine tests, especially given the potential sequelae of a false-positive urine test result.

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