Metabolite profiling of synthetic cathinones: towards the identification of consumption biomarkers in forensic and clinical settings

The emergence of new psychoactive substances (NPS) in the recreational drug market constitutes a risk in terms of public health and poses challenges at forensic and clinic contexts. Synthetic cathinones are the second largest group of NPS reported worldwide.1 However, the unavailability of suitable analytical methods and reference standards for the detection of cathinones and/or their metabolites to support forensic and clinical identifications means that most new cathinones often remain undetected/undetected in routine drug screening methods.

In this work we have used high resolution mass spectrometry to evaluate metabolic stabilities and to identify the metabolite profiles upon incubation of multiple cathinones (Figure 1) with human liver microssomes.2 With the ultimate goal of having a proactive stance towards the NPS problem, in addition to already reported cathinones (e.g. 4-CIC, 3-CMC, 4-CMC and 4-MEAP), we have synthesized four synthetic cathinones (3-CIC, 4-MDMB, 4-MNEB and 4-MDMP) for which the emergence on the NSP market is expected to be eminent, due not only to their easy synthesis, from available raw materials, but also due to their structural resemblance to other already reported synthetic cathinones.

Based on the calculation of pharmacokinetic parameters such as half-life and intrinsic clearance, 4-MEAP is estimated to be a high clearance compound and all the remaining synthetic cathinones selected for this study are intermediate clearance compounds.3 This fact anticipates the key role of metabolites as suitable biomarkers to extend detection windows beyond those provided by parent cathinone. A metabolic pathway common to all cathinones was the reduction of the-keto group and the N-dealkylation, from the parent cathinone and/or from the reduced metabolite. Hydroxylation on the alkyl chain was also detected. The glucuronic acid conjugation to the reduced metabolite constituted the sole Phase II transformation identified.

To our knowledge this study constitutes a first-hand metabolite profiling of the already reported synthetic cathinones 4-CIC, 3-CMC and 4-CMC. The fact that 3-CMC accounts for almost a quarter of the quantity of powders seized during 2020 is noteworthy.4 In addition, we have synthesized and characterized the metabolites of four synthetic cathinones for which the emergence in the recreational drug market is highly probable. The analytical methods developed along with the synthetic cathinones, and metabolites characterized are now available, to be included in routine screening methods to attest the consumption of the cathinones selected for this study.