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تسجيل

Drugs and other toxins

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  P212-213

2026-10-14

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Drugs and other toxins

Interpretation of the concentrations of drugs in postmortem blood and tissue specimens is complicated because many drugs are unstable in vivo and in vitro. Interpretation may also be affected by tolerance, inter-individual variation in pharmacological response, drug interactions, the presence or absence of natural disease and the circumstances under which death occurred. For example, cocaine is hydrolysed readily before and after death. It is thought that serum cholinesterase is responsible for the hydrolysis of cocaine to ecgonine methyl ester, while the formation of benzoylecgonine may arise from spontaneous nonenzymatic hydrolysis (Isenschmid et al. 1989). Interpretation must therefore depend not only on the concentration of cocaine measured, but also of benzoylecgonine and ecgonine methyl ester. Even when postmortem blood is collected into a tube that contains sodium fluoride (to retard in vitro hydrolysis of the cocaine), the degree of hydrolysis that occurs post mortem compared with that prior to death is almost impossible to determine. In other words, if relatively high concentrations of cocaine metabolites are detected, it can be difficult to determine whether they resulted from an acute overdose of cocaine or from chronic heavy consumption (bingeing) over a period of several hours or even days. Even if that question could be answered, it is known that cocaine can cause serious and even fatal cardiac arrhythmias at high concentrations, but it is also known that regular cocaine users can snort or inject large doses of cocaine without apparent, serious, short-termtoxicity. Incontrast, some individuals can develop excited delirium syndrome and die after relatively small doses of cocaine. Some benzodiazepines (e.g. flunitrazepam, nitrazepam and clonazepam) are known to be unstable in vitro and back-calculation of the perimortem concentration is not practical (Robertson and Drummer 1995, 1998). Many other drugs are known to have poor stability in postmortem blood (e.g. chlordiazepoxide, phenelzine, olanzapine, zopiclone). Morphine glucuronide may be converted back into un conjugated morphine in postmortem blood in circumstances in which sufficient bacterial contamination is present to release glucuronidase (Carroll et al. 2000).