Is "levamisole" always levamisole in adulterated cocaine? Answer through analysing human biological samples with enantioselective high-performance liquid chromatography and supercritical fluid chromatography coupled with tandem mass spectrometry.

Abstract

Over many years, it was believed that (street) cocaine was adulterated with levamisole despite several studies indicating that the actual adulterant was its racemic analogue tetramisole. The reason for the misinterpretation of earlier results could be the fact that the mass spectrometric detector cannot differentiate between levamisole and tetramisole. The enantiomers of tetramisole must be first separated and identified using an enantioselective technique before mass spectrometric detection. Therefore, one of the major goals of the present study was to develop methods for the enantioselective determination of tetramisole and to use it in the analysis of blood, urine, oral fluid, hair and viscera samples of cocaine abusers. In addition, this study also addresses the dispute on the metabolites of tetramisole present in the same biological samples. The third goal of the present study was to evaluate the applicability of enantioselective supercritical fluid chromatography coupled with tandem mass spectrometry for forensic and clinical toxicology purposes. As the results indicated, cocaine is mostly adulterated not with levamisole but with its racemic analogue tetramisole. The study confirms that both aminorex and 4-phenyl-2-imidazolidinone co-exist as metabolites of tetramisole in human biological matrices, contributing to the ongoing clarification of the metabolic fate of tetramisole in humans. 4-Hydroxytetramisole was detected in all biological matrixes, which proves that this specific metabolite can be used as a biomarker of the consumption of tetramisole.

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