Does Lidocaine Cause False Positive Results on Cocaine Urine Drug Screen? Public

Abstract

BACKGROUND: Individuals who have tested positive for cocaine have claimed that lidocaine, or its primary metabolite norlidocaine (monoethylglycinexylidide (MEGX)), have caused false positive results for the cocaine metabolite benzoylecgonine (BE) on urinary immunoassay testing. 

OBJECTIVE: The goal of the study was to determine if lidocaine exposure from routine medical procedures can result in false positives on a commercially available cocaine immunoassay urine drug screen (UDS). 

METHODS: We performed a cross-sectional observational study of patients receiving lidocaine as part of their regular care. Standard immunoassay drug screens and confirmatory liquid chromatography-mass spectrometry (LC-MS) were performed on all urine samples to assess for MEGX and BE. 

RESULTS In total, 121 patients were positive for lidocaine and negative for BE. One hundred and fourteen of these patients were also positive for MEGX. None of these patients tested positive for cocaine on the UDS (95% CI: 0% - 3.7% for the full sample and 0% - 3.9% for the 114 who tested positive for MEGX). 

CONCLUSION: The present study found no evidence that lidocaine or norlidocaine are capable of producing false positive results on standard cocaine urine immunoassays.

Table of Contents

Introduction......................................................................................................................1-5

Methods……......................................................................................................................5-8

Statistical Analysis............................................................................................................8

Results..............................................................................................................................8-10

Discussion........................................................................................................................11-12

Limitations.......................................................................................................................12-13

Conclusion.......................................................................................................................13

References Cited.............................................................................................................14-16

About this Honors Thesis

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School	Emory College
Department	Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Chemistry, Biochemistry Biology, General Biology, Physiology
Mot-clé	Cocaine Norlidocaine Lidocaine False Positive Urine Drug Screen
Committee Chair / Thesis Advisor	Morgan, Brent, Emory University
Committee Members	Soria, Jose, Emory University Corces, Victor, Emory University

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