Enantioselective determination of methylone and its major phase 1 metabolites in various biological matrices and stereochemical stability of methylone enantiomers.

Abstract

Many publications investigate drug concentration in various matrices aiming to select the most suitable matrix for bioanalytical studies. When for chiral drugs these studies are performed using nonenantioselective analytical methods they do not provide information about ratio of enantiomers in different matrices. A previously developed enantioselective high-performance liquid chromatography-mass spectrometry method was used for the analysis of methylone and its major phase 1 metabolites in plasma, urine, oral fluid, and sweat collected from a controlled clinical study. Along with the traditional representation of results as concentration-time dependence, the ratio of enantiomers was also plotted versus time. The concentration of methylone in oral fluid was higher compared with its concentration in circulating blood. The concentration of R-(+)-methylone was higher compared with S-(-)-methylone, and the enantiomeric excess was different in different matrices. In addition, stereochemical stability of methylone was found to be matrix dependent and surprisingly less in plasma compared with that in whole blood. Because of its higher concentration and higher stability in oral fluid, methylone is detectable in this matrix over a longer period of time after its administration than in any other studied matrices. The enantiomeric ratio in oral fluid is higher compared with that in plasma. In contrast to methylone, the concentration of methylone metabolites in oral fluid, except dihydromethylone, is lower than in plasma. The correlations of methylone concentrations in different matrices are fragile, with rather high interindividual variation, and cannot serve for reliable determination of time elapsed after drug administration. SIGNIFICANCE STATEMENT: This study demonstrates that oral fluid is a superior matrix for detecting methylone due to its higher concentration and greater stereochemical stability compared with plasma and other matrices. Enantioselective analysis reveals matrix-dependent stereochemistry and highlights that metabolite patterns differ from the parent drug. These findings emphasize the importance of matrix choice and enantioselective monitoring for accurate pharmacokinetic assessment and provide critical insights for interpreting drug detection and timing in forensic and clinical settings.