Fenfluramine: An Uncommon Cause of False Positive Urine Drug Testing: A Case Report

Background

Fenfluramine is an antiseizure medication approved by the Food and Drug Administration for the treatment of Dravet syndrome in patients older than 2 years. Fenfluramine is an amphetamine derivative. It cross-reacts with amphetamines in urine drug screen immunoassays.

Patient Presentation

A 2-year-old patient with Dravet syndrome had a cardiorespiratory arrest and tested positive for amphetamines in a urine drug screen, raising concerns of child abuse. Liquid chromatography–mass spectrometry confirmed the presence of fenfluramine but did not detect amphetamines.

Conclusion

Fenfluramine can result in a false-positive amphetamine urine drug screen at the recommended dose for Dravet syndrome. Awareness of this potential cross-reactivity can prevent undue child protective services reports, especially in patients at high risk for sudden death.