Author: Jared Castle
Castle, Jared, 2020 The stability of selected psychoactive drugs in simulated post-mortem blood, Flinders University, College of Science and Engineering
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The presence or absence of psychoactive medication in post-mortem specimens is important to establish to determine medication adherence or potential drug intoxication in coronial investigations. This thesis examined the stability of 17 selected antipsychotic and antidepressant drugs. Liquid chromatography coupled to diode array detection (LC-DAD) analytical methods were optimised and validated for the analysis of these drugs in human whole blood. Drug stability was assessed in blood preserved (with 2 % w/v sodium fluoride) and unpreserved; and inoculated (with faecal microorganisms) or non-inoculated. Their stability was evaluated at: -20 °C and 4 °C, to simulate specimen/body storage; room temperature, relevant to specimen handling; and 37 °C, relevant post-death and in warm climates.
Dominant microorganisms present in inoculated blood specimens throughout the 37 °C experiments were identified using 16S rRNA sequencing as previously reported dominant species in post-mortem specimens, indicating the methodology used to simulate post-mortem blood was suitable. Preservation did not prevent community changes over time in all preserved specimens, indicating sodium fluoride alone may not limit microbial activity for some species. There was a significant difference between microbial communities based on temperature, sodium fluoride presence, and the interaction between these factors, indicating that communities present in authentic post-mortem specimens may vary depending on the environment of the body after death, the time at which specimens are collected, and how specimens are stored and handled.
The greater instability of chlorpromazine, fluphenazine, prochlorperazine, and flupentixol, and reduced formation of some degradation products, at -20 °C than at 4 °C, after a year, indicates it may be preferable to refrigerate and not freeze specimens. N-dealkylation degradation products were detected for many drugs. However, this degradative pathway is unlikely to affect the interpretation of casework analyses unless degradation rates are considerably enhanced in authentic post-mortem specimens.
Lurasidone degraded until undetected in inoculated, unpreserved blood specimens stored at room temperature and 37 °C. Degradation products were characterised by liquid chromatography coupled to quadrupole-time-of-flight-mass-spectrometry (LC-QTOF-MS), followed by comparison to standards synthesised by Tristan Fraser [1]. Unambiguous identification was not achieved. Nevertheless, the major degradation product was detected in retrospectively analysed casework data. Risperidone, which degraded at a similar rate in the
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same experiments, is known to degrade in post-mortem specimens until only its degradation product may be detected [2, 3]. The major lurasidone degradation product should therefore be included in coronial screening methods as a marker of lurasidone administration. FSSA now utilises the major lurasidone degradation product to indicate cases where lurasidone concentrations may be underestimated.
Ziprasidone was unstable in all blood specimens stored at room temperature and 37 °C. It was indicated that ziprasidone may react with carbonyl species present in blood, and that the resultant degradation products may further degrade due to microbial activity and then degrade to unknown products. This highlights that ziprasidone may not be reliably detected in post-mortem casework. Due to limited casework data available for review, it remains to be determined if the degradation products detected should be used as indicators of the ante-mortem administration of ziprasidone.
Keywords: post-mortem toxicology, antipsychotic, antidepressant, stability, lurasidone, ziprasidone, drug degradation, forensic toxicology
Subject: Forensic & Analytical Chemistry thesis
Thesis type: Doctor of Philosophy
Completed: 2020
School: College of Science and Engineering
Supervisor: Paul Kirkbride