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ADVANCING TOWARDS MULTIDISCIPLINARY INTEGRATION:
PHARMACOGENETICS' ROLE IN FORENSIC TOXICOLOGY
Rajabov Shukhrat Yunusovich
Assistant at the Alfraganus University
Expert at the Tashkent city branch of the Scientific and Practical Center of Forensic
Medical Expertise of the Republic of Uzbekistan
Email: dr.oydinov@gmail.com
https://doi.org/10.5281/zenodo.11174500
Abstract
Pharmacogenetics investigates how DNA genes respond individually to drug administration.
With advancements in genome sequencing and molecular genetics, pharmacogenetic research
has gained traction, offering insights beyond medical applications. It emerges as a valuable tool
in deciphering toxicological data in post-mortem examinations, pivotal for determining causes
and circumstances of death. This systematic literature review aims to sensitize the forensic
community to the potential of pharmacogenetics and provide a procedural guide for forensic
toxicologists dealing with drug-related fatalities of uncertain origins. The review encompassed
searches with keywords like 'pharmacogenetics' and 'forensic toxicology', yielding 125 articles,
with 29 meeting inclusion criteria. The majority (75%) were original articles (n = 21), while
25% were case reports (n = 7). Among the studies, 78% (n = 22) involved deceased individuals
subjected to complete autopsies, with the remaining 22% (n = 6) focusing on healthy subjects
administered drugs for subsequent pharmacogenetic analysis. Opioids (codeine, morphine,
methadone) were the most studied drugs, followed by antidepressants (tricyclic
antidepressants, venlafaxine). Across the studies, there was consistent emphasis on the
indispensability of pharmacogenetic assessments in drug-related deaths, particularly in cases
not involving drug overdose. This review underscores the significance of forensic
pharmacogenetics, a field within toxicology that remains incompletely understood yet proves
invaluable in sudden deaths, overdoses, drug administration-related fatalities, and cases of
alleged medical negligence.
Keywords
: pharmacogenetics, forensic toxicology, multidisciplinary approach, molecular
autopsy, drug-related death.
Introduction
Forensic science, a multidisciplinary field drawing from chemistry, physics, and biology,
operates to establish the "weight of evidence". Within this interdisciplinary framework, the
forensic toxicology laboratory is tasked with detecting and measuring drugs and other chemical
substances in biological fluids collected during autopsies. Additionally, toxicological
assessments serve medico-legal purposes, such as drug and alcohol testing for commercial
driver licensing or addressing occupational medicine concerns arising from worker exposure
to toxic agents.
In forensic toxicology, understanding the pivotal role of pharmacogenetics is imperative.
Pharmacogenetics, the study of genetic variations influencing drug response, affects
pharmacokinetics, pharmacodynamics, and ultimately drug bioavailability. In forensic
pathology, the determination of cause of death relies on crime scene investigations, medical
history, autopsies, and toxicological findings. In this context, pharmacogenetics emerges as a
valuable tool in deciphering toxicological puzzles, particularly in cases of suicides, accidents,
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and deaths of unknown etiology. Moreover, the potential impact of pharmacogenetics on drug
metabolism should be considered when interpreting post-mortem substance concentrations in
bodily fluids or organs.
The term 'pharmacogenetics' describes the study of genetic variations influencing drug
pharmacokinetics or pharmacodynamics. These variations may affect genes encoding
transporter proteins, drug-metabolizing enzymes, receptors, etc. Pharmacogenetics aims to
predict individual drug responses and assess their effects. In clinical practice, it helps evaluate
a patient's capacity to achieve desired therapeutic effects or, conversely, to encounter adverse
reactions. Advances in genome sequencing and molecular genetics have propelled
pharmacogenetic research, serving to identify disease-specific genes, gene products, and allelic
variants influencing therapeutic responses.
Furthermore, pharmacogenetics serves as a crucial tool in interpreting toxicological data in
post-mortem examinations, often vital in determining cause and manner of death. Forensic
pathologists frequently encounter deaths associated with drug use or abuse. For instance, the
CYP2D6 gene plays a role in metabolizing certain drugs like morphine and its derivatives
(codeine, tramadol, dihydrocodeine, oxycodone), with certain CYP2D6 polymorphisms
impacting methadone clearance. Similarly, CYP3A4 is involved in benzodiazepine and
buprenorphine metabolism. Thus, identifying cytochrome-inducing or -suppressing mutations
can provide insights in cases of suspected drug overdose-related deaths.
Moreover, pharmacogenetics can serve as a vital instrument in elucidating the analysis of
toxicological data during post-mortem examinations, often pivotal in ascertaining both cause
and manner of death. Notably, forensic pathologists frequently encounter cases involving drug
and narcotic use/abuse. For instance, the CYP2D6 gene, part of the Cytochrome P450 Family 2
Subfamily D, participates in metabolizing various drugs like morphine and its derivatives
(codeine, tramadol, dihydrocodeine, oxycodone), with specific CYP2D6 polymorphisms
potentially impacting methadone clearance. Similarly, CYP3A4 is implicated in metabolizing
benzodiazepines and buprenorphine. Hence, identifying the presence of cytochrome-inducing
or -suppressing mutations can offer insights into cases of suspected drug overdose-related
deaths.
Materials and Methods
A systematic review was undertaken.
SCOPUS served as the search engine from January 1, 1980, to August 1, 2021, to investigate the
correlation between pharmacogenetics and forensic toxicology. The search employed the
following keywords: (pharmacogenetics) AND (forensic toxicology); (pharmacogenetics) AND
(post-mortem); (pharmacogenetics) AND (forensic sciences); and (pharmacogenetics) AND
(autopsy). The exclusion criteria were as follows: (1) review articles, (2) articles not written in
English, (3) abstracts, (4) posters, and (5) conference communications. The inclusion criteria
comprised: (1) Original Articles, (2) Case Reports, (3) Articles written in English, (4) In Vivo
Studies, and (5) In Vitro Studies.
Results
More than 75% of the included studies (n = 29) were original articles (n = 22), while
approximately 25% were case reports (n = 7). Among the included studies, 22 involved
complete autopsies, while around 20% (n = 6) focused on healthy individuals who had died
after drug administration followed by pharmacogenetic analysis. Opioids (such as codeine,
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morphine, and methadone) were predominantly utilized in the analyzed cases, followed by
antidepressants (including tricyclic antidepressants and venlafaxine). Notably, only one study
administered ethylenediaminetetraacetic (EDTA) anticoagulant and organophosphorus drugs.
Blood analysis was conducted in all cases except one, where a hair sample was used to analyze
genetic polymorphism. Additionally, one report analyzed various post-mortem samples, such
as saliva, spleen, and buccal swabs. Gas chromatography-mass spectrometry (GC-MS) emerged
as the primary method for toxicological investigation, followed by liquid chromatography-mass
spectrometry (LC-MS). Gas chromatography (GC) and high-performance liquid
chromatography (HPLC) were utilized in two studies. Furthermore, only one study employed
tandem mass spectrometry (UPLC-MS/MS) for toxicological investigation.
Discussion
Forensic pharmacogenetics delves into the examination and analysis of genotypes and allelic
variations of genes encoding enzymes crucial in drug metabolism. This review's findings affirm
that one extensively studied gene is CYP2D6, a member of the cytochrome P450 enzyme
superfamily. Due to genetic polymorphisms within the CYP2D6 gene, four primary phenotypes
emerge: ultra-rapid metabolizers (UM), extensive metabolizers (EM), poor metabolizers (PM)
lacking functional enzymes due to defective or deleted genes, and intermediate metabolizers
(IM) possessing alleles that partially reduce enzyme activity [58]. A recent review [59]
indicated that 7% of individuals succumbing to opioid overdoses exhibited an ultra-rapid
phenotype, intensifying the toxic effects. As outlined in Table 1, the forensic interest in
genotyping this cytochrome stems from its involvement in metabolizing opioids and analogous
drugs. Notably, it plays a pivotal role in metabolizing endocannabinoid
arachidonoylethanolamide (anandamide), 20-hydroxyeicosatetraenoic acid ethanolamide (20-
HETE-EA), and 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid ethanolamides (EpETrE-EAs),
potentially modulating the endocannabinoid system signaling. Its polymorphisms are well-
documented to influence the metabolism of fatty acids, steroids, and retinoids. Furthermore, its
involvement in the oxidative metabolism of drugs such as adrenoceptor antagonists,
antiarrhythmics, and tricyclic antidepressants has been established.
The CYP2D6 gene, like all enzymes within the CYP class, participates in hepatic phase I
metabolism of foreign substances and drugs. The P450 family converts drugs into electrophilic
intermediates, which are subsequently conjugated by phase II enzymes (e.g., UDP
glucuronosyltransferase and N-acetyltransferase) before being excreted. While at least 60 P450
genes exist, the most extensively studied subsets include CYP1A2, CYP2A6, CYP2B6, CYP2C19,
CYP2D6, CYP2E1, and CYP3A4, responsible for metabolizing the majority of prescription and
over-the-counter drugs.
Conclusion
The implementation of pharmacogenetics carries significant implications from both medical-
legal and ethical perspectives. Addressing concerns surrounding informed consent and the
collection of DNA databases is paramount prior to integrating genetic analysis into forensic
institutions. Moreover, a key issue revolves around the informativeness of genetic testing,
which may lead to uncertainties regarding paternity. Consequently, reluctance from relatives
to consent to pharmacogenetic testing could hinder the establishment of truth. In light of
applying pharmacogenetics in forensic science, these considerations must be carefully weighed
in both practical applications and research endeavors. Similarly, adopting a multidisciplinary
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approach is imperative in the forensic field, necessitating its incorporation into routine forensic
practices. This necessity is underscored by the findings of this systematic review, offering
forensic teams a structured workflow to navigate cases involving suspected drug-related
deaths.
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