Postmortem Toxicology: Redistribution, Tolerance and Cause-of-Death (UGC-NET Unit IV)

Advanced UGC-NET Forensic Science Unit IV drill on postmortem toxicology with a sharp focus on the three interpretation pillars that decide whether a measured drug level can be called the cause of death. Postmortem redistribution (PMR) coverage spans the volume-of-distribution (Vd) and tissue-to-blood ratio mechanism, the central-to-peripheral concentration gradient that builds after death, the PMR coefficient (ratio of postmortem to antemortem concentration), and the practical preference for femoral vein blood over cardiac blood in toxicology sampling. Specific PMR profiles for amitriptyline and other tricyclic antidepressants, digoxin, fentanyl, methadone, cocaine and other lipophilic basic drugs are covered with reference to Pounder and Jones (1990, Forensic Science International) and Skopp review series. Tolerance coverage spans pharmacokinetic induction, receptor down-regulation, the gulf between opioid-naive and chronic-user fatal thresholds (Singapore methadone maintenance studies, fentanyl thresholds), and the therapeutic-toxic-lethal reference range concept. Cause-of-death interpretation covers polypharmacy synergy (opioid plus benzodiazepine respiratory depression, TCA QT prolongation), positional asphyxia with drug-on-board, drug-disease interaction (cocaine plus cardiomyopathy), autopsy findings (pulmonary oedema, foam cone, needle marks), histology, vitreous-humour ethanol confirmation, artefactual ethanol from microbial neoformation, embalming and decomposition challenges, and the joint pathologist plus toxicologist interpretation model. Indian context covers NFSU and AIIMS forensic-toxicology research and the Indian forensic medicine textbook tradition.