Identification and stability of synthetic cathinones in biological samples

Synthetic cathinones (“bath salts”) are a class of novel psychoactive substances abused for their psychostimulant and euphoric effects. However, these drugs have received international and national attention due to severe and life threatening adverse effects. In order to properly associate pharmacological, impairing, or toxic effects with synthetic cathinone use, toxicologists must be able to detect and reliably interpret results. The detection of these synthetic phenethylamines relies on validated analytical techniques. Quantitative assays determine the concentration of drug present in biological samples at the time of analysis, which may be significantly different from the concentration at the time of collection or time of death. Drug stability must be understood in order to determine the extent to which these changes influence analytical results. This research provides the forensic toxicology community with a comprehensive understanding of the stability of these compounds in biological matrices.

A method for the detection of twenty-two synthetic cathinones, isolated from blood and urine using liquid chromatography quadrupole/time of flight mass spectrometry (LC-Q/TOF MS) was developed and validated. This method was used to assess synthetic cathinone stability in blood (pH 7) and urine (pH 4 and 8) stored at 32°C, 20°C, 4°C, and -20°C for six months. The selected synthetic cathinones were representative of the various structural analogs, including unsubstituted secondary amines (methcathinone, ethcathinone, buphedrone, and pentedrone); ring substituted secondary amines (3-FMC, 4-FMC, 4-MEC, 4-EMC, 3,4-DMMC, mephedrone, and methedrone); methylenedioxy-substituted secondary amines (methylone, ethylone, butylone, pentylone, eutylone); and tertiary amines (α-PVP, naphyrone, pyrovalerone, MPBP, MDPBP, and MDPV). The significance of analyte, storage temperature, storage time, concentration, and matrix pH were systematically assessed.

Stability was influenced by structure, matrix pH, and storage temperature. Halogenated cathinones (3-FMC, 4-FMC) were the least stable and the tertiary cathinones bearing the methylenedioxy group (MDPBP, MDPV) were the most stable. The analysis of authentic urine samples from cathinone users supported these experimental findings. Matrix pH and cathinone structure had a more profound influence than prolonged storage.

In addition to detecting synthetic cathinones from antemortem specimens to support experimental stability findings, synthetic cathinones were also identified in a series of fifty fatalities to determine postmortem distribution and redistribution. Drugs were identified in central and peripheral blood, urine, liver, vitreous humor, and stomach contents. Central to peripheral blood (C/P) and liver to peripheral blood (L/P) ratios were determined for seven synthetic cathinones to assess postmortem redistribution (PMR). While synthetic cathinones appear to exhibit low to moderate PMR, the highest C/P ratios were observed for cathinones bearing a secondary amine and a methylenedioxy group.