Postmortem Drug Redistribution Research Articles

Postmortem Drug Redistribution: A Compilation of Postmortem/Antemortem Drug Concentration Ratios.

Postmortem drug redistribution (PMR) is a well-known phenomenon in forensic toxicology with implications for medico-legal death investigations. Paired antemortem (AM) specimen and postmortem (PM) mortuary admission femoral blood drug concentrations from 811 coronial cases were used to construct a retrospective compilation of PM/AM drug concentration ratios for 42 parent drugs and metabolites. The median PM/AM ratios for all antidepressants were > 1 and consistent with PMR In contrast, the median PM/AM ratios of most benzodiazepines were < 1. The antipsychotics were varied (0.63-3.3) and suggest the mixed effects of PMR and drug instability. Amphetamines exhibited no trends (0.90-0.95) and are likely confounded by many factors. The PM/AM ratios of cardiovascular drugs, opioids and other drugs are also reported. This research represents an expansive retrospective compilation of paired AM and PM drug concentrations for many toxicologically relevant drugs. While the median PM/AM ratios demonstrate some drug-dependent trends, there was no obvious relationship between AM specimens and PM femoral blood taken at mortuary admission.

A Mechanism-Based Forensic Investigation into the Postmortem Redistribution of Morphine.

The interpretation of postmortem drug levels is complicated by the change in drug blood levels during the postmortem period, a phenomenon known as postmortem drug redistribution. We investigated the postmortem redistribution (PMR) of morphine, morphine-3-glucuronide and normorphine in the rat. Morphine (10mg/kg) was intravenously injected into rats, followed by euthanasia 1h post-injection. The carcasses were placed in a supine position at room temperature, and tissues including heart blood, femoral blood, liver, lung and brain were collected at different time points: 0, 8, 16 or 24h postmortem. The samples were analyzed with a validated (following modified Scientific Working Group for Forensic Toxicology (SWGTOX) (20) guidelines) liquid chromatography-tandem mass spectrometry method. The use of a mechanism-based approach (involving the used set doses of drug with the study performed in controlled environment) to assess PMR using systematic and statistical analyses provides important information that has not previously been presented in PMR literature. While previous human studies focus on central to peripheral ratios as well as peripheral to tissue ratio, this work focused on the change in morphine and metabolite concentrations over the course of the postmortem interval in relation to each other in addition to the comparison to additional matrices at each postmortem interval. Postmortem redistribution was identified in several tissues across the postmortem interval; however, there was minimal statistical difference observed among each matrix at a given postmortem interval with the exception of normorphine and morphine-3-glucuronide. Combined, our study provides a valuable resource and reference information that can aide toxicologists, medical examiners or coroners when assessing postmortem drug concentrations of morphine and metabolites when they are making determinations of cause of death.

Postmortem redistribution of triazolam, alprazolam, delorazepam (chlordesmethyldiazepam) and zolpidem in a suicide case

Summary Postmortem drug redistribution (PMR) is a well-recognized phenomenon which affects the concentration of drugs inside the various body tissues and organs, possibly determining misled interpretation of postmortem drug concentrations. In contrast, drug levels in peripheral blood are commonly considered to be comparable with antemortem concentrations. The difference between central and peripheral blood concentrations is known as the “central to peripheral ratio” (C/P). Drugs with high C/P ratios are associated with potential for PMR. In several forensic cases, PMR should be taken into account for the correct estimation of drug blood levels at the moment of death, especially when multiple psychotropic drugs have been co-ingested. In the case reported hereby, the PMR of several benzodiazepines including triazolam, alprazolam, and delorazepam (chlordesmethyldiazepam) plus zolpidem was evaluated in a fatal multidrug suicide case. A 38-year-old man was found dead in his apartment. On the scene, many packaging of pharmaceutical drugs were found. During the autopsy, no evidence of natural disease nor trauma was found to account for his death. Heart (central) and femoral (peripheral) blood, urine and vitreous humor were collected and submitted to toxicological analysis. Delorazepam, triazolam and zolpidem were detected at therapeutic levels in peripheral blood while alprazolam and ethanol were found at toxic levels. The potential synergistic sedative effect of multiple benzodiazepines intake, combined to high ethanol concentration, produced a condition compatible with fatal intoxication. C/P ratio for the tested compounds ranged from 1.22 (alprazolam) to 1.47 (delorazepam) demonstrating moderate PMR for these drugs. This is the first report in which the PMR of delorazepam is discussed.

Post-mortem toxicology: A pilot study to evaluate the use of a Bayesian network to assess the likelihood of fatality

The challenge of interpreting post-mortem drug concentrations is well documented and relies on appropriate sample collection, knowledge of case circumstances as well as reference to published tables of data, whilst taking into account the known issues of post-mortem drug redistribution and tolerance. Existing published data has evolved from simple data tables to those now including sample origin and single to poly drug use, but additional information tends to be specific to those reported in individual case studies. We have developed a Bayesian network framework to assign a likelihood of fatality based on the contribution of drug concentrations whilst taking into account the pathological findings. This expert system has been tested against casework within the coronial jurisdiction of Sunderland, UK. We demonstrate in this pilot study that the Bayesian network can be used to proffer a degree of confidence in how deaths may be reported in cases when drugs are implicated. It has also highlighted the potential for deaths to be reported according to the pathological states at post-mortem when drugs have a significant contribution that may have an impact on mortality statistics. The Bayesian network could be used as complementary approach to assist in the interpretation of post-mortem drug concentrations.

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 (1 mg/kg) was injected into anesthetised rabbit; after 1 h, 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 three 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 and abdominal fat, liver, bone marrow and skeletal muscle were taken. The samples were analysed with a validated LC-MS/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 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.

P56: Effect of variation in site and time on the level of ethanol and methanol in postmortem blood samples

Introduction It is well recognized that postmortem (PM) drug levels in blood may be unstable as a consequence of redistribution artifact. Whereby drugs diffuse from their binding sites of high concentration in tissues and major organs, such as liver and lung, into blood. Also drugs can be expected to diffuse from gastric contents into blood. When measuring drug concentrations after death, it is important to consider the phenomenon of PM drug redistribution. PM drug concentrations may not be a true reflection of the ante mortem one and as a result, wrong conclusions could be made about the cause of death. There is few published evidence for most drugs and poisons to show the important differences in their PM concentrations in blood and tissues according to choice of sampling site, sampling time, handling of samples including containers, preservation and documentation and type of laboratory investigation carried out on PM samples. Aim The present work was carried out to evaluate experimentally in rabbits PM behavior of ethyl and methyl alcohol in relation to their concentration in different blood sampling sites at different time intervals. Furthermore to assess the effect of site blood sampling on the level of ethyl alcohol and methyl alcohol at time of autopsy in human cadavers and compare it with the results from rabbit experiments. Methods The study was conducted on ninety male rabbits as experimental animals, and the human cadavers that were positive on screening to ethanol (n=4) and methanol (n=3) during the period of the study. Rabbits were divided into three groups (30 rabbits each), two groups for each drug, which were given the LD50 of the drug. Blood samples were drawn from right and left sides of the heart and femoral vein from each group of rabbits, immediately, twelve hours and twenty-four hours after death. As regards human cadavers, blood samples (5m1) were drawn from right and left sides of the heart and femoral vein at time of autopsy. Experimental and human blood sample extracts were analyzed by gas chromatography. Results The study showed that ethanol was detected in the control group after 12h PM with increased concentration overtime. The highest mean value recorded was 681 μg/ml in 24h PM. No significant changes could be detected in immediate PM blood ethanol concentration (BEC) from different sampling sites. Though PM BEC increased significantly over time for the three sampling sites, yet up to 24h PM, the femoral (peripheral) BEC was the closest to the immediate PM value. Concerning methanol, the study showed also that no significant changes could be detected in immediate PM blood methanol concentration (BMC) from different sampling sites. Similarly, it increased over time for different sampling sites, where within 12h , femoral (peripheral) blood was the only site that didn’t alter significantly and could be used as a reliable indicator for the immediate PM BMC concentration. The results obtained from the human cases were generally in reasonable agreement with those of rabbit experiments. Conclusion Experimental animal studies, when interpreted carefully, are indicative of the PM drug changes observed in human, denoting that femoral (peripheral) blood is the best site for drug sampling.

Liver and peripheral blood concentration ratio (L/P) as a marker of postmortem drug redistribution: a literature review

The liver to peripheral blood (L/P) ratio, based upon review of previously published works, was evaluated as a marker of postmortem redistribution (PMR). Literature supported the proposed model that drugs exhibiting an L/P ratio of less than 5 are prone to little or no PMR, while those with an L/P ratio greater than 20-30 have propensity for significant redistribution. Many antidepressants, including both tricyclic antidepressants and selective serotonin re-uptake inhibitors, were markedly differentiated from drugs previously verified to be free from, or exhibit little, PMR. The magnitude of the liver to blood concentrations also appeared to provide an advantage over the conventional central to peripheral blood ratio model of PMR by demonstrating a wide range of values (1.6-97) for interpretation of drugs' potential for, and variations in, redistribution.

A review of the use of clozapine levels to guide treatment and determine cause of death

To review the literature to examine the use of clozapine levels to (i) guide therapy and prevent toxicity in clinical care and (ii) determine cause of death in post-mortem examination of patients who were treated with clozapine. MEDLINE was searched in December 2010 using the following keywords: 'clozapine levels', 'clozapine and toxicity', 'clozapine and death', 'clozapine and mortality' and 'post-mortem redistribution'. Data was also collected from the 2010 MIMS Annual. The literature reported significant variation in clozapine levels attained with any given dose, and considerable variability in the clinical response achieved at any given clozapine level. The lowest effective clozapine levels ranged from 250 to 550 µg/L, while the recommended upper limit to prevent toxicity varied from 600 to 2000 µg/L. There was minimal correlation between clozapine levels and side effects, with the exception of sedation, hypotension and seizure activity. The risk of seizures increased with plasma clozapine levels greater than 600 µg/L or rapid upward titration. In addition to prescribed dose, there are many factors that influence plasma clozapine levels. After death, the process of post-mortem drug redistribution resulted in 3.00 to 4.89 times increases in clozapine levels in central blood vessels and 1.5 fold increases in peripheral vessels compared to ante-mortem levels. The exact range of clozapine levels that corresponds to toxicity remains unclear. However, levels between 350 µg/L and 1000 µg/L achieved with gradual upward titration are more likely to be effective and less likely to cause toxicity. Ongoing clozapine level monitoring is indicated, especially when (i) prescribing higher doses (> 600 mg/day) of clozapine, (ii) there has been a change in a patient's concomitant pharmacotherapy or cigarette use and (iii) there has been a suboptimal response to treatment. The use of post-mortem clozapine levels to determine clozapine toxicity as a cause of death is unreliable.

Book of the Month: Karch's Pathology of Drug Abuse

Book of the Month: Karch's Pathology of Drug Abuse

Alternate strategies for postmortem drug testing.

Alternate strategies for postmortem drug testing.

Discrepancy between CYP2D6 phenotype and genotype derived from post-mortem dextromethorphan blood level

Objective: To describe the death of a toddler after a therapeutic dose of dextromethorphan and its investigation. Study design: Case report, cytochrome P450 phenotype and genotype determination in the victim and post-mortem drug redistribution study performed in rats. Results: A 20-month Asian male who received 3 mg of dextromethorphan once at 09:00 h and again at 22:00 h was found dead at 04:35 h. Post-mortem examination showed signs of early bronchopneumonia (bacterial cultures were negative); dextromethorphan and dextrorphan blood concentrations taken from the heart cavity were 500 ng/ml (1.84 μmol/l) and 200 ng/ml (0.78 μmol/l), respectively. Despite the dextromethorphan level being almost 100-fold higher than expected after therapeutic doses, intentional or unintentional overdose was extremely unlikely; other potential causes were investigated. Post-mortem drug redistribution study performed in rats showed that dextromethorphan does not undergo extensive redistribution after death (6±5-fold increase) and could not explain the observed dextromethorphan level. The dextromethorphan/dextrorphan concentration ratio of 2.5 found in this toddler was compatible with a slow CYP2D6 metabolizer phenotype. However, the toddler exhibited a fast metabolizer genotype. Potential reasons for this discrepancy are discussed. Conclusion: CYP450 phenotypes derived from post-mortem blood levels should be interpreted with caution and preferably confirmed by a genotype analysis.

Postmortem Drug Redistribution—Human Cases Related to Results in Experimental Animals

Femoral blood is widely accepted as the most reliable postmortem specimen for drug analysis in forensic toxicology. There is considerable evidence that the drug concentrations in peripheral blood samples are closer to the antemortem level than the concentration in cardiac blood. In the present study drug concentrations measured in postmortem femoral and/or heart blood samples from eight cases were compared with the concentration found in serum samples from the same subject collected antemortem or perimortem. The drugs involved were amitriptyline, nortriptyline, imipramine, verapamil and chloroquine. Two additional cases with very early postmortem blood samples, as well as femoral blood samples from later autopsy, involved amphetamine and tetrahydrocannabinol. The results from the human cases were compared with results from rat experiments on similar drugs. The samples were analyzed by high performance liquid or gas chromatography. The cases with tricyclic antidepressants had a median postmortern femoral blood to antemortem serum drug concentration ratio of 3.3, the 95% reference range being from 1.1 to 6.0 (pooled data). Large variations of the ratios were seen. The extremes noted were a postmortem femoral blood to antemortem serum drug concentration ratio of 0.9 in a case with nortriptyline and 49 in the case with chloroquine. The low ratio in the former case could be due to attempted resuscitation, while the high ratio in the latter case is probably due to the extremely high apparent volume of distribution and a high blood to plasma concentration ratio for chloroquine. Accordingly, it is dubious whether the drug concentration found in femoral blood at autopsy can be accepted as being representative for the antemortem level. The results obtained from the human cases in the present study were generally in reasonable agreement with previous rat experiments, confirming that the animal studies when interpreted carefully, are indicative of the changes observed in man as well as a previous study in pigs. Studies on drug concentrations in pigs are not necessarily more representative for the findings in humans than experiments with a smaller animal like the rat. The postmortem concentration changes observed for tetrahydrocannabinol in man were found to be unpredictable, while in the accompanying experimental rat study there was a significant postmortem decrease in the tetrahydrocannabinol blood concentration measured in blood from the inferior vena cava. In special cases where the diagnosis of overdose is to be used as judicial evidence, a single sample of blood may prove insufficient. In such cases, analyses of several samples of blood and tissue will increase the possibility of reaching a correct conclusion, but reference values on drug concentrations in tissues are often missing.

A Fatality Involving Clothiapine and Clomipramine

A fatality resulting from the suicidal ingestion of clothiapine, clomipramine and biperiden is reported. Clomipramine, its metabolite N-desmethylclomipramine and clothiapine were quantified in blood, liver, kidney and gastric contents by HPLC and GC. Biperiden was detected only in the gastric content. Significant differences of drug levels were found in postmortem blood obtained from brain and from heart. Concentrations of clomipramine and N-desmethylclomipramine ranged from 0.48 to 1.61 mg/L and 0.26 to 1.32 mg/L, respectively, and clothiapine from 0.50 to 2.15 mg/L. This phenomenon may reflect a postmortem drug redistribution.

Postmortem release of amitriptyline from the lungs; a mechanism of postmortem drug redistribution

An experimental rat model was used to study postmortem redistribution of amitriptyline (AMI). Two hours after a subcutaneous injection with 20 mg of amitriptyline, the rats ( n = 40) were anaesthetized and blood samples were drawn from the femoral vein and the heart. The rats were then sacrificed by CO 2 and left at room temperature for either 0.1, 1, 2, 5, 24, 48, or 96 h. Postmortem blood samples from the heart and the inferior vena cava, and tissue samples from the lungs, heart, liver, right kidney, thigh muscle, the wall of the abdominal vena cava and brain were analyzed by high performance liquid chromatography. A significant increase was observed within 2 h postmortem in heart blood and later also in blood from the inferior vena cava. At 96 h postmortem the concentration increase was 4.4 ± 0.5-fold ( P < 0.01) and 3.0 ± 1.1-fold ( P < 0.05) as compared to the antemortem values observed in heart blood and blood from the inferior vena cava, respectively (mean ± SEM). In the lungs there was a fall in the concentration of AMI from 148 ± 16.7 μmol/kg at 0.1 h to 49.1 ± 7.8 μmol/kg at 96 h postmortem ( P < 0.01). In the vessel wall of the abdominal vena cava there was also a significant fall in drug concentration, while in heart muscle and liver an increase in drug concentration was observed. In animals where the lungs were removed agonally ( n = 7), the drug concentration in heart blood had increased significantly less at 2 h postmortem. Accordingly, this animal model demonstrates that postmortem drug release from the lungs play an important role in the phenomenon of postmortem drug redistribution.

Diffusion as a mechanism of postmortem drug redistribution: an experimental study in rats.

In some cases of drug overdose there is a reservoir of unabsorbed drug in the stomach and gut. Furthermore, agonal aspiration might establish a second reservoir in the lungs. Two experimental rat models were used to study if diffusion from these reservoirs could contribute to the phenomenon of postmortem drug redistribution. Overnight fasted rats were sacrificed by CO2 and 75 mg of amitriptyline (AMI) was administered by a gastric tube. In the first series (n = 19), the tubes were removed after AMI administration. In the second series (n = 17), the trachea was ligated and cut prior to drug administration to prevent airways contamination. The rats were left at room temperature on their back for a period of 5, 10, 24, 48, 96 up to 192 h and samples of heart blood, blood from the inferior vena cava, tissue samples from heart, lungs, different liver lobes, kidney and psoas muscle were taken. In both series of rats we observed that as early as 5 h postmortem increasing concentrations of amitriptyline were found in the liver lobes lying closest to the stomach. In rats where the trachea was not ligated, drug contamination of the lungs also resulted in an increase in drug concentration within 5 h in heart blood and heart muscle. In rats where the trachea had been ligated, amitriptyline was found in the lungs after 96 h postmortem. The main metabolite nortriptyline was also detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Post-mortem drug redistribution — A toxicological nightmare

Detailed human case data is presented to illustrate the dramatic extent of the phenomenon of post-mortem drug redistribution. The data suggests that there is a post-mortem diffusion of drugs along a concentration gradient, from sites of high concentration in solid organs, into the blood with resultant artefactual elevation of drug levels in blood. Highest drug levels were found in central vessels such as pulmonary artery and vein, and lowest levels were found in peripheral vessels such as subclavian and femoral veins. In individual cases, in multiple blood samples obtained from ligated vessels, concentrations of doxepin and desmethyldoxepin ranged from 3.6 to 12.5 mg/l and 1.2 to 7.5 mg/l, respectively; amobartital, secobarbital and pentobarbital from 4.3 to 25.8 mg/l, 3.9 to 25.3 mg/l and 5.1 to 31.5 mg/l respectively; clomipramine and desmethylclomipramine from 4.0 to 21.5 mg/l and 1.7 to 8.1 mg/l, respectively and flurazepam 0.15 to 0.99 mg/l; imipramine and desipramine from 4.1 to 18.1 mg/l and 1.0 to 3.6 mg/l, respectively. We conclude that this poorly studied phenomenon creates major difficulties in interpretation and undermines the reference value of data bases where the site of origin of post-mortem blood samples is unknown.