Stability of mephedrone and five of its phase I metabolites in human whole blood

Abstract

Mephedrone is a new psychoactive substance known to be unstable in biological matrices stored at room temperature or refrigerated. While the instability of mephedrone has been investigated before, there is currently no data regarding the stability of mephedrone metabolites. In this study, a liquid chromatography–tandem mass spectrometry method for the simultaneous quantification of mephedrone and five of its phase I metabolites (dihydro‐mephedrone, nor‐mephedrone, hydroxytolyl‐mephedrone, 4‐carboxy‐mephedrone and dihydro‐nor‐mephedrone) in human whole blood has been developed and validated. Samples were extracted by a mixed mode solid‐phase extraction and analyzed on a pentafluorophenylpropyl column. The method was successfully validated for selectivity, linearity (0.2–2 to 10–100 ng/mL), limits of detection (50–500 pg/mL) and quantification (200–2000 pg/mL), precision (0.924–8.27%), accuracy (86.6–115%), carryover, recovery (32.5–88.3%), and matrix effects (71.0–108%). Analyte stability in human whole blood preserved with sodium fluoride/potassium oxalate was assessed at +4°C and −20°C after 24 hours, 48 hours, 4 days, and 10 days of storage. Instability was observed in samples stored at +4°C: nor‐mephedrone and 4‐carboxy‐mephedrone lost 40.2 ± 6.7% and 48.1 ± 4.8%, respectively, of their initial concentration at low concentration level and 33.8 ± 4.2% and 44.6 ± 6.5%, respectively, at high concentration level after 10 days. All analytes were more stable at −20°C where the highest loss of 22.6 ± 6.9% was observed for 4‐carboxy‐mephedrone after 10 days. This is the first time stability of mephedrone metabolites in human whole blood has been assessed, indicating −20°C to be the recommended storage condition for all analytes in clinical settings.

Retrospective analysis of new psychoactive substances in blood samples of German drivers suspected of driving under the influence of drugs

“…[17][18][19]21,22 In accordance with Tuv et al 18 and Wille et al 21 In contrast to previous studies determining the prevalence of NPS in DUID cases ( Another potential influence on the study's prevalence is the possible instability of NPS, particularly synthetic cathinones, in blood. [7][8][9][10][11][12][13][14][15] To reduce drug loss, many authors investigating the stability of NPS in blood recommended −20 C to be the best storage condition. 8,10,[13][14][15] Therefore, all samples were stored frozen prior to analysis.…”

“…[7][8][9][10][11][12][13][14][15] To reduce drug loss, many authors investigating the stability of NPS in blood recommended −20 C to be the best storage condition. 8,10,[13][14][15] Therefore, all samples were stored frozen prior to analysis. However, the long storage time of up to 2.5 years may have negatively affected the calculated concentrations as well as the detection rate resulting in a prevalence which is probably too low.…”

“…Other analytical problems include the lack of reference standards and the need for sensitive methods to detect even low concentrations in biological samples. Furthermore, the possible instability of many NPS [7][8][9][10][11][12][13][14][15] has to be considered when interpreting toxicological findings.…”

Pharmacokinetics of Mephedrone Enantiomers in Whole Blood after a Controlled Intranasal Administration to Healthy Human Volunteers

“…Whole blood samples were collected from six participants but for the purpose of this study, samples from five participants (referred to here as M2-M6) were analysed. Whole blood samples from participant M1 were discarded due to stability concerns [19] as they had been collected five months before the chiral analysis commenced.…”

Extended Stability Evaluation of Selected Cathinones

“…Sunlight and heat are known to degrade the cathinone in Catha edulis into dimers or inactive metabolites (Chappell and Lee, 2010;Katz et al, 2014). Stability research on cathinone's synthetic derivatives tells a similar story, with many synthetic cathinones showing some degree of instability based on storage temperature and sample matrix (Sørensen, 2011;Tsujikawa et al, 2012;Al-Saffar et al, 2013;Concheiro et al, 2013;Johnson and Botch-Jones, 2013;Maskell et al, 2013;Soh and Elliott, 2014;Busardò et al, 2015;Kerrigan, 2017, 2018;Miller et al, 2017;da Cunha et al, 2018;Adamowicz and Malczyk, 2019;Czerwinska et al, 2019;Nowak et al, 2020). Understanding the consequences of this variability on subsequent interpretations of data derived from samples suspected to contain synthetic cathinones is crucial.…”