Postmortem redistribution of the heroin metabolites morphine and morphine-3-glucuronide in rabbits over 24 h

The interpretation of postmortem drug levels is complicated by changes in drug blood levels in the
postmortem period, a phenomena known as postmortem drug redistribution. We investigated the
postmortem redistribution of the heroin metabolites morphine and morphine-3-glucuronide in a
rabbit model. Heroin (1mg/kg) was injected into anesthetised rabbit, after 1 hour an auricular vein
blood sample was taken and the rabbit was euthanised. Following death rabbits were placed in a
supine position at room temperature and divided into 3 groups namely 1) immediate autopsy, 2)
autopsy after 30 minutes and 3) autopsy 24 h after death. Various samples which included femoral
blood, cardiac blood, lung, liver, kidney, vitreous humour, subcutaneous & abdominal fat, liver,
bone marrow and skeletal muscle were taken. The samples were analysed with a validated LCMS/MS
method. It was observed that within minutes there was a significant increase in free
morphine postmortem femoral blood concentration compared to the antemortem sample (0.01 ±
0.01 mg/L to 0.05 ± 0.02 mg/L).Various other changes in free morphine and metabolite
concentrations were observed during the course of the experiment in various tissues. Principal
component analysis was used to investigate possible correlations between free morphine in the
various samples. Some correlations were observed but gave poor predictions (>20% error) when
back calculating. The results suggest that rabbits are a good model for further studies of postmortem
redistribution but that further study and understanding of the phenomena is required before accurate
predictions of the blood concentration at the time of death are possible.