The influence of collection site and methods on postmortem morphine concentrations in a porcine model

This study was to determine the relationship of antemortem to postmortem morphine concentrations in heart and femoral blood in a porcine model following acute intravenous opiate overdose. The study involved 20 swine; each was sacrificed 10 min after injection of 2 mg/kg body weight of morphine. Drug concentrations were assayed from vitreous humor and blood isolated from the femoral vein and artery and left and right ventricles at various times postmortem. Comparisons were made between antemortem and postmortem values to determine agreement and reliability. Both free and total postmortem values varied significantly among animals, sampling sites, and over time. Free postmortem values were generally higher in comparison with antemortem values, whereas postmortem total morphine values were similar to or slightly lower than antemortem values. The effect of time on postmortem values was small. These results demonstrate a significant amount of variability in free and total morphine measurements both over time and within and between sites. Furthermore, a comparison of antemortem to postmortem values demonstrates a lack of consistency relative to the dose of morphine administered. Concentrations of morphine in the femoral vein were typically the lowest observed. This observation is not surprising given the transformation that occurs prior to the drug reaching the femoral vein. Values associated with diffuse tissues, relative to femoral veins, demonstrate more stochastic variation.