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Phencyclidine is one of the drugs of abuse included in qualitative urine drug screens that are frequently ordered in the emergency department despite concerns about specificity and clinical utility. Many drugs have been described to cause false-positive results for phencyclidine. We present 2 cases of false-positive phencyclidine qualitative urine drug screen results in patients with seizures from tramadol misuse or abuse. The involvement of tramadol and its active metabolite, N-desmethyltramadol, was confirmed by in vitro testing. These cases illustrate that tramadol and its metabolites can trigger a false-positive phencyclidine urine drug screen result in nonfatal cases and highlight the lack of specificity of the phencyclidine qualitative urine drug screen. Copyright © 2011 American College of Emergency Physicians. Published by Mosby, Inc. All rights reserved.


Binh T Ly, Stephen L Thornton, Colleen Buono, Judith A Stone, Alan H B Wu. False-positive urine phencyclidine immunoassay screen result caused by interference by tramadol and its metabolites. Annals of emergency medicine. 2012 Jun;59(6):545-7

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PMID: 21924518

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