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Cocaine adulteration with the anthelminthic tetramisole (levamisole/dexamisole): long-term monitoring of its intake by chiral LC-MS/MS analysis of cocaine-positive hair samples


Madry, Milena M; Kraemer, Thomas; Baumgartner, Markus R (2019). Cocaine adulteration with the anthelminthic tetramisole (levamisole/dexamisole): long-term monitoring of its intake by chiral LC-MS/MS analysis of cocaine-positive hair samples. Drug Testing and Analysis, 11(3):472-478.

Abstract

Recent studies indicate that not only the anthelminthic levamisole but also the racemate tetramisole (R-/S-phenyltetraimidazothiazole, PTHIT) was found as adulterant for cocaine. We herein report on the investigation of the prevalence of PTHIT among cocaine-positive hair samples and the discrimination of the presence of its stereoisomers levamisole and dexamisole. Cocaine-positive hair samples were collected in a forensic context in 2015 and mainly 2017 (n=724). Cocaine and PTHIT concentrations have been determined by achiral liquid chromatography-tandem mass spectrometry (LC-MS/MS). For distinction of levamisole/dexamisole chiral LC-MS/MS was performed. Cocaine hair concentrations ranged from 500 (cut-off) to approximately 800,000 pg/mg. The study demonstrates a strong prevalence of PTHIT in cocaine users' hair (87 %, n=627). PTHIT hair concentrations ranged from below LLOQ 3.5 to approximately 61,000 pg/mg (median: 260 pg/mg). Surprisingly, enantiomeric ratios of levamisole/dexamisole ranged from 0.17 to 1.34 (median: 0.63). Therefore, PTHIT-adulterated street cocaine samples (n=24) seized between 2013 and 2016 were tested. Samples mainly contained racemic tetramisole (87.5 %), only one sample contained levamisole only and two samples contained non-racemic PTHIT. Our experiments suggest that the presence of tetramisole in biological samples may have hitherto been underestimated. Most probably higher dexamisole than levamisole concentrations in hair specimens arise from stereoselective metabolism and/or elimination. This is particularly important in light of the different pharmacological activities of the two enantiomers and potentially different adverse effects. Toxicological interpretations in intoxication cases with adulterated cocaine should not only consider levamisole but also tetramisole and terminology in scientific contributions should be used accordingly.

Abstract

Recent studies indicate that not only the anthelminthic levamisole but also the racemate tetramisole (R-/S-phenyltetraimidazothiazole, PTHIT) was found as adulterant for cocaine. We herein report on the investigation of the prevalence of PTHIT among cocaine-positive hair samples and the discrimination of the presence of its stereoisomers levamisole and dexamisole. Cocaine-positive hair samples were collected in a forensic context in 2015 and mainly 2017 (n=724). Cocaine and PTHIT concentrations have been determined by achiral liquid chromatography-tandem mass spectrometry (LC-MS/MS). For distinction of levamisole/dexamisole chiral LC-MS/MS was performed. Cocaine hair concentrations ranged from 500 (cut-off) to approximately 800,000 pg/mg. The study demonstrates a strong prevalence of PTHIT in cocaine users' hair (87 %, n=627). PTHIT hair concentrations ranged from below LLOQ 3.5 to approximately 61,000 pg/mg (median: 260 pg/mg). Surprisingly, enantiomeric ratios of levamisole/dexamisole ranged from 0.17 to 1.34 (median: 0.63). Therefore, PTHIT-adulterated street cocaine samples (n=24) seized between 2013 and 2016 were tested. Samples mainly contained racemic tetramisole (87.5 %), only one sample contained levamisole only and two samples contained non-racemic PTHIT. Our experiments suggest that the presence of tetramisole in biological samples may have hitherto been underestimated. Most probably higher dexamisole than levamisole concentrations in hair specimens arise from stereoselective metabolism and/or elimination. This is particularly important in light of the different pharmacological activities of the two enantiomers and potentially different adverse effects. Toxicological interpretations in intoxication cases with adulterated cocaine should not only consider levamisole but also tetramisole and terminology in scientific contributions should be used accordingly.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Legal Medicine
Dewey Decimal Classification:340 Law
610 Medicine & health
Uncontrolled Keywords:Analytical Chemistry, Spectroscopy, Pharmaceutical Science, Environmental Chemistry
Language:English
Date:March 2019
Deposited On:02 Oct 2018 15:14
Last Modified:23 Mar 2019 02:01
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:1942-7603
OA Status:Closed
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1002/dta.2505
PubMed ID:30239147

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