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Characterization of an Amphetamine Interference from Gabapentin in an LC-HRMS Method
Ana Celia Muñoz-Muñoz1, Teresa Pekol1, Dana Schubring1
1Research and Development, Dominion Diagnostics LLC, 211 Circuit Drive, North Kingstown, RI 02852, USA.
Journal of Analytical Toxicology
|July 3, 2019
Summary
A gabapentin fragment mimics amphetamine in LC-HRMS urine drug tests, causing false positives. This study identifies the interference and details a method to mitigate its impact on drug testing accuracy.
Area of Science:
- Clinical Chemistry
- Forensic Toxicology
- Analytical Chemistry
Background:
- Liquid chromatography-high-resolution mass spectrometry (LC-HRMS) is crucial for multi-drug testing in urine.
- Accurate identification of drugs and metabolites is essential for patient care and forensic analysis.
- Interferences in analytical methods can lead to false-positive or false-negative results, compromising test integrity.
Purpose of the Study:
- To identify and characterize an amphetamine interference observed during the development of a urine drug testing LC-HRMS method.
- To investigate the source of the interference, which was found to be related to gabapentin.
- To describe mitigation strategies for this specific interference in LC-HRMS analysis.
Main Methods:
- Development of a multi-class LC-HRMS method for the detection of 47 drugs and metabolites in urine.
- Investigation of interferences by analyzing patient specimens with high gabapentin concentrations.
- Characterization of in-source fragmentation patterns using high-resolution mass spectrometry.
- Modification of the LC-HRMS method to resolve the interference.
Main Results:
- An interference mimicking amphetamine was detected, passing qualitative criteria for amphetamine.
- The interference was directly correlated with high concentrations of gabapentin in patient urine samples.
- The source of the interference was identified as a gabapentin in-source fragment that is isomeric with protonated amphetamine.
- The developed mitigation strategy successfully removed the interference from the analytical results.
Conclusions:
- Gabapentin can cause significant interference in LC-HRMS urine drug testing, leading to potential false-positive amphetamine results.
- Understanding drug fragmentation and potential interferences is critical for developing robust analytical methods.
- Method modifications are necessary to ensure the accuracy and reliability of drug testing in the presence of common medications like gabapentin.
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