Simultaneous analysis of four endocannabinoids and endocannabinoid congeners together with delta-9 tetrahydrocannabinol and related metabolites in dried blood spots

In the medical field, the endocannabinoid system is both a difficult and hot topic for scientific and media reasons (cannabis, cannabidiol, etc.). Due to their instability and low concentrations in blood and physicochemical properties, the complexity of endocannabinoid assay is previously reported in different matrices. This study aims to report a LC-MS/MS method for the simultaneous quantification of four endocannabinoids and endocannabinoid congeners: N-arachidonoylethanolamide (anandamide or AEA), 2-arachidonoylglycerol/1-arachidonoylglycerol (2-AG/1-AG), oleoylethanolamide (OEA) and palmitoylethanolamide (PEA), together with Δ9-tetrahydrocannabinol (THC) and its main metabolites [11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) and 11-hydroxy- Δ9-tetrahydrocannabinol (11-OH THC] in Dried Blood Spot (DBS). This validated method reported LLOQs of 0.1 µg/L for AEA, 0.5 µg/L for THC and 11-OH THC, and 1 µg/L for OEA, PEA, 2AG and THC-COOH. The method demonstrated intra- and interassay accuracy and precision of less than 20 % for the LLOQ, and less than 15 % for the other calibration points. In particular, the stability carried out in this study demonstrated the practical applicability of DBS for the measurement of endocannabinoids in the whole blood. Therefore, we propose this method as a tool for basic and clinical research to support the growing interest of the scientific community in the endocannabinoid system.