Key concepts in postmortem drug redistribution

Postmortem redistribution (PMR) refers to the changes that occur in drug concentrations after death. It involves the redistribution of drugs into blood from solid organs such as the lungs, liver, and myocardium. Drug properties such as volume of distribution, lipophilicity, and pKa are important factors. Basic, highly lipophilic drugs with a volume of distribution greater than 3 l/kg are most likely to undergo PMR. Examples include the tricyclic antidepressants, digoxin, and the amphetamines. The anatomical location of blood sampling can influence the drug concentration. The ideal site is a ligated or clamped femoral vein. Medical toxicologists participating in forensic cases involving drugs likely to undergo PMR must be aware of its potential contribution to the postmortem drug concentration. Correlation with laboratory data and any available antemortem or perimortem clinical information is necessary to render an appropriate opinion on the cause of death.