Stability of Synthetic Cathinones in Blood

Journal of Analytical Toxicology, 2017;41:711–719 doi: 10.1093/jat/bkx071 Advance Access Publication Date: 31 August 2017 Article Article Stability of Synthetic Cathinones in Blood Lindsay Glicksberg and Sarah Kerrigan* Department of Forensic Science, Sam Houston State University, Huntsville, TX, USA *Author to whom correspondence should be addressed. Email: Abstract The synthetic cathinones are powerful psychostimulants that have been associated with impairment, intoxication and fatal overdose. Forensic laboratories must be able to identify these new drugs as part of antemortem and postmortem toxicology investigations. Preliminary reports have indicated that some of the synthetic cathinones are unstable in biological matrices. It is important to understand drug stability in biological evidence so that analytical findings can be interpreted appropriately. The objective of this study was to systematically evaluate the concentration, temperature and analyte-dependent stability of synthetic cathinones in preserved blood using liquid-chromatography/ quadrupole-time of flight-mass spectrometry (LC/Q-TOF-MS). Cathinone stability was investigated at frozen, refrigerated, ambient and elevated temperature (−20°C, 4°C, 20°C and 32°C). Although no concentration dependent differences in stability were observed, cathinone stability was highly temperature and analyte-dependent. Substituents on the aromatic ring and nitrogen profoundly influenced stability. Tertiary amines (pyrrolidinyl analogs) were significantly more stable than their N-alkylated (secondary amine) counterparts. Furthermore, the methylenedioxy (MD) group also exerted a significant stabilizing effect, for both secondary and tertiary amines. The unsubstituted and ring-substituted secondary amines were the least stable, most notably 3-fluoromethcathinone (3-FMC). Under some conditions, significant losses were observed within hours of storage. Half-lives ranged from a little as 8 h (3-FMC) to 21 days (3,4-methylenedioxy-α-pyrrolidinobutiophenone, MDPBP) at elevated temperature (32°C). In contrast, half-lives ranged from 0.4 to >10 months when refrigerated and demonstrated even greater stability when frozen. Biological evidence may be subjected to a variety of environmental conditions prior to, and during transport to the laboratory. These findings highlight the need to consider the potential for both temperature and analyte-dependent differences. Due to the inherent instability of certain drugs within the class, quantitative drug findings in toxicological investigations must be interpreted with caution, and within the context of specimen storage and integrity. Introduction The synthetic cathinones are powerful amphetamine-like psychostimulants that have increased in popularity in the USA since 2009 (1). According to the Drug Enforcement Administration, cathinones were reported in 48 of the 50 states in 2015, with the highest number of reports occurring in the South and Midwest regions. In 2010, the most common cathinones in the USA were mephedrone, methylenedioxypyrovalerone (MDPV) and methylone (2). From 2013 to 2015 however, methylone, α-pyrrolidinopentiophenone (α-PVP) and ethylone accounted for 91% of all reports. In addition to increased drug seizures, illicit drug manufacturers produce new cathinones as part of their ongoing attempt to circumvent drug laws and evade judicial consequences. This is evidenced by the fact that the number of synthetic cathinones encountered in the National Forensic Laboratory Information System increased from 5 in 2009 to 35 in 2015. The sought-after effects of these drugs include increased energy, empathy, openness and libido. However, cardiac, psychiatric and neurological effects are common among users that require medical intervention. Over the past decade, the federal government has taken numerous steps to ban specific synthetic cathinones and the © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: 711 712 majority of states have enacted legislation, often in the form of general class bans, in an effort to curb their appeal. These compounds present a challenge to the forensic toxicology community due to the number of structurally related analogs and regioisomers that currently exist. The cathinones are β-keto amphetamines (2-aminopropiophenones) that can be categorized into Nalkylamines (secondary amines) and pyrrolidines (tertiary amines). The chemical properties of these arylaminoketones are dominated by two functional groups: the ketone and the amine. The cathinones are either ring-substituted (R1 and R2), formed by the variation of the α-carbon substituent (R3), or N-alkylated (R4 and R5) (Figure 1). At the inception of this study, a total of 22 synthetic cathinones were commercially available and the individual structures of these compounds are shown in Figure 2. Drug stability must be carefully considered when interpreting toxicological results (3). Pre-analytical conditions, including specimen transport, storage and handling may cause the drug concentration to change. The stability and intrinsic chemical properties of many illicit and pharmaceutical drugs are widely known and understood, but this information is relatively limited for the synthetic cathinones. An increased understanding of cathinone stability is needed due to the prevalence of these drugs in criminal and death investigations (4–9). Forensic toxicology laboratories go to considerable lengths to ensure the precision and accuracy of their quantitative results. However, in order to reliably interpret those results, drug stability and pre-analytical changes in drug concentration should be carefully considered. While the proliferation of cathinone compounds over the past decade has renewed interest in the stability of synthetic cathinones, the instability of cathinone (its natural precursor) has been understood for decades. Cathinone was first identified in the 1970s as the principle pharmacologically active compound in “khat”. Although its degradation product (cathine) had been identified years earlier, the delay in the identification of cathinone was largely due to its instability in the plant material (10–13). Cathinone was also reported to be unstable in basic conditions (11, 14). More recently, Tsujikawa, et al. investigated the stability of five synthetic cathinones in aqueous solutions over a range of pH. They concluded that drug stability increased with decreasing pH and that the rate of decomposition was likely dependent on the chemical structure (14). Cathinone instability was also observed during gas chromatography–mass spectrometry (GC–MS) analysis. Under some conditions cathinones can thermally degrade, resulting in the formation of oxidative breakdown products (15–17). There are a relatively small number of studies that have addressed synthetic cathinone stability in blood or plasma. Morad et al. was the first to report that cathinone was unstable (...truncated)