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Metabolism of levamisole and kinetics of levamisole and aminorex in urine by means of LC-QTOF-HRMS and LC-QqQ-MS

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Abstract

The antihelminthic drug Levamisole can enhance cocaine effects by conversion into the amphetamine-like drug aminorex. We describe an LC-MS method for the determination of levamisole and its metabolite aminorex in human urine. Selectivity is given, calibration curves were linear within the calibration range 2.5–250 ng/mL; limits of the method were LoD 0.51 ng/mL, LoQ 1.02 ng/mL for levamisole and LoD 0.65 ng/mL, LoQ 0.76 ng/mL for aminorex. Precision data was in accordance with the guidelines (intraday precision for aminorex ranged between 5.75 and 11.0 % for levamisole between 8.36 and 10.9 %; interday precision for levamisole 10.9–16.9 % and for aminorex 7.64–12.7 %; accuracy data for levamisole −1.96 to –14.3 % and for aminorex−11.9 to–18.5 %). The validated method was successfully applied to study the urinary excretion of levamisole after the administration of 100 mg of levamisole orally. Levamisole and aminorex could be detected in post-administration urine samples. Levamisole could be detected up to 39 h after ingestion, while aminorex was detectable up to 54 h. Maximum aminorex concentrations were 45 ng/mL urine. Further metabolites of levamisole after oral ingestion by means of liquid chromatography hybrid quadrupole time-of-flight high-resolution mass spectrometry (LC-QTOF-HRMS) were identified. Only 0.5 % of the ingested drug was quantified as unchanged levamisole in urine. Besides aminorex, five isomers of aminorex and 4 hydroxy-metabolites of aminorex or its isomers were found. Furthermore, levamisole is also hydroxylated and eliminated free or conjugated with sulfate or glucuronide into urine.

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Correspondence to Cornelius Hess.

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Hess, C., Ritke, N., Broecker, S. et al. Metabolism of levamisole and kinetics of levamisole and aminorex in urine by means of LC-QTOF-HRMS and LC-QqQ-MS. Anal Bioanal Chem 405, 4077–4088 (2013). https://doi.org/10.1007/s00216-013-6829-x

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  • DOI: https://doi.org/10.1007/s00216-013-6829-x

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