Metabolism and Analysis of Desomorphine

Abstract

Desomorphine is a semi-synthetic opioid that is ten times more potent than morphine, with a faster onset but shorter duration of action. It is a major component of the drug referred to as “Krokodil”, which is used as a heroin substitute. Its prevalence is difficult to estimate due to a lack of analytically confirmed cases, which may in part be due to the limited studies regarding its pharmacology or methodology to detect the drug in biological specimens. This research seeks to further the understanding of both desomorphine’s metabolism and its detection in biological specimens, to facilitate its identification in clinical and forensic toxicology laboratories. Six commercially available enzyme-linked immunosorbent assays were evaluated to determine their effectiveness with respect to desomorphine detection. Cross-reactivities were highly variable between assays, ranging from <2.5-77%. Recombinant human cytochrome P450 enzymes (rCYPs) and recombinant uridine 5'-diphospho-glucuronosyltransferases (rUGTs) were used to investigate the biotransformational pathways involved in desomorphine metabolism. Phase I metabolism could be attributed to seven rCYPs (rCYP2B6, rCYP2C8, rCYP2C9, rCYP2C18, rCYP2C19, rCYP2D6 and rCYP3A4), producing a total of nine phase I metabolites (nordesomorphine, desomorphine-N-oxide, two norhydroxydesomorphine isomers, and five hydroxylated isomers). During phase II metabolism, desomorphine-glucuronide was produced by nine rUGTs (rUGT1A1, rUGT1A3, rUGT1A8, rUGT1A9, rUGT1A10, rUGT2B4, rUGT2B7, rUGT2B15, and rUGT2B17). Chemical and enzymatic hydrolysis of conjugated metabolites were investigated using desomorphine-glucuronide generated in situ using rUGT enzyme. Acid hydrolysis and five β-glucuronidase sources (BGTurbo™, IMCSzyme™, Escherichia coli, Helix pomatia and Patella vulgata) were evaluated. Acid hydrolysis produced complete hydrolysis of desomorphine-glucuronide, and under optimal conditions, each enzyme produced complete or near complete hydrolysis (≥96%), with BGTurbo™ and IMCSzyme™ offering the shortest incubation times. Under simulated challenging conditions, P. vulgata was the most effective enzyme evaluated. Desomorphine was analyzed in blood and urine samples using gas chromatography-mass spectrometry (GC-MS), and urine samples were additionally analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and liquid chromatography-quadrupole/time of flight-mass spectrometry (LC-Q/TOF-MS). Each method was validated in accordance with published guidelines for forensic use. Additionally, LC-Q/TOF-MS was used to analyze desomorphine metabolites, which in the absence of commercially available reference material or authentic urine specimens, were generated in-vitro.