Just Say No to Postmortem Drug Dose Calculations

Abstract

AbstractIt has long been known that forensic and clinical toxicologists should not determine the dose of a drug administered based on postmortem blood drug concentrations but to date there has been limited information as to how unreliable these dose calculations can be. Using amitriptyline as a model drug this study used the empirically determined pharmacokinetic variables for amitriptyline from clinical studies and clinical, overdose (where the individual survived) and death (ascribed to amitriptyline toxicity) case studies in which the dose of drug administered or taken was known. Using these data, standard pharmacokinetic equations and general error propagation it was possible to estimate the accuracy of the consumed dose of amitriptyline compared to the actual dose consumed. As was expected in postmortem cases, depending on the pharmacokinetic equation used, the accuracy (mean +128 to +2347 %) and precision (SD ± 383 to 3698%) were too large to allow reliable estimation of the dose of drug taken or administered prior to death based on postmortem blood drug concentrations. This work again reinforces that dose calculations from postmortem blood drug concentrations should not be carried out.