THE ANALYSIS OF DRUGS AND THEIR METABOLITES IN CLINICAL AND POST-MORTEM SAMPLES

Abstract

The analysis of clinical and post-mortem samples for drugs and their metabolites is an important step in the investigation and management of individuals who may have been exposed to these compounds. Clinical urine samples may be submitted for drugs of abuse (DoA) analysis. Post-mortem blood and urine analysis may be required as part of a Coronial investigation. DoA analysis typically involves a screening assay, followed by confirmation using a second assay. Measurement of post-mortem samples usually involves a screen to identify the compounds present, before the concentrations of any toxicologically significant compounds are measured using separate assays. The work in this thesis aims to determine if these two-step processes can be consolidated into single assays and the effect that this will have on the quality and utility of the results generated. Liquid chromatography-high resolution mass spectrometry (LC-HRMS) was used to develop an assay which can measure 38 drugs and their metabolites in urine samples. An LC-HRMS assay was also developed to screen post-mortem blood and urine samples for 1100 compounds and to simultaneously measure the concentration of 42 compounds. Both assays were subjected to a full validation. Retrospective analysis of results achieved following 18 months of use of the DoA assay revealed that 0.01, 0.003 and 0.02% of methadone, buprenorphine and diazepam results respectively were likely to be affected by sample adulteration. 22% of samples contained a gabapentinoid. Data from the analysis of post-mortem samples revealed a 125 % increase in the number of instances of a compound being detected by LC-HRMS and a 60 % increase in the number of compounds detected by the LC-HRMS screen. Analysis of the turnaround times for morphine pre and post LC-HRMS screen implementation showed a 55% and 47% reduction in turnaround time for total and free morphine respectively and a reduction in the amount of staff time to screen a batch of samples for total and free morphine of 2 days. The LC-HRMS assays detected fentanyl and carfentanyl with 100 and 89% sensitivity respectively. In conclusion, two assays have been developed which are suitable for the screening of drugs of abuse in urine samples and for the screening and simultaneous quantitation of post-mortem blood and urine samples. These assays reduce turnaround times and the resources required for analysis, and improve the quality of the results generated.

Date of Award	1 Aug 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Anthony Freemont (Supervisor)