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

Difficulties associated with the interpretation of postmortem toxicology

While postmortem (PM) toxicology results provide valuable information towards ascertaining both the cause and manner of death in coronial cases, there are also significant difficulties associated with the interpretation of PM drug levels. Such difficulties are influenced by several pharmacokinetic and pharmacodynamic factors including PM redistribution, diffusion, site-to-site variability in drug levels, different drug properties and metabolism, bacterial activity, genetic polymorphisms, tolerance, resuscitation efforts, underlying conditions, and the toxicity profile of cases (i.e. single- or mixed-drug toxicity). A large body of research has been dedicated for better understanding and even quantifying the influence of these factors on PM drug levels. For example, several investigative matrices have been developed as potential indicators of PM redistribution, but they have limited practical value. Reference tables of clinically relevant therapeutic, toxic, and potentially fatal drug concentrations have also been compiled, but these unfortunately do not provide reliable reference values for PM toxicology. More recent research has focused on developing databases of peripheral PM drug levels for a variety of case-types to increase transferability to real-life cases and improve interpretations. Changes to drug levels after death are inevitable and unavoidable. As such, guidelines and practices will continue to evolve as we further our understanding of such phenomena.

Atypical postmortem redistribution in chronic methadone consumers

Available literature demonstrates that methadone is prone to moderate postmortem redistribution, but subject to high interindividual variability in the central to peripheral blood concentration ratios (C/P). In this case series, 10 cases of chronic methadone users displaying C/P < 1 (range 0.26-0.82) are described. Femoral, cardiac and ante-mortem blood concentrations of methadone and its metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) are reported for all cases, as well as sex, age, case history, results of the pathological investigation, other toxicological findings and cause and manner of death. EDDP blood concentrations, similar in both central and peripheral blood, as well as antemortem blood concentration results in Case 4, demonstrate that this atypical C/P < 1 finding is attributable to postmortem changes and not analytical or pre-analytical artifacts. Case 4 is a particularly instructive example, with femoral blood concentration (966 ng/mL) approximately twice as high as cardiac blood (499 ng/mL) and ante-mortem blood (418 ng/mL, collected 38 min prior to death)-clearly demonstrating that cardiac blood methadone concentration is more representative of the antemortem blood concentration in this case. In Case 4 and four others, toxicological interpretation based on femoral blood concentration alone would have been misleading. Based on these results and evidence from the literature, it is hypothesized that methadone bioaccumulates in the tissues of chronic users and redistributes from thigh tissues into femoral blood, increasing the concentration postmortem. This case series highlights how femoral blood is not always preserved from postmortem changes and that the analysis of multiple blood sources is necessary to avoid a misleading toxicological interpretation-particularly for cases of chronic methadone users.

Using μX-Ray CT to observe postmortem diffusion from the stomach in a rat model

The stomach has long been recognised as a depot for postmortem diffusion. A better understanding of the phenomena of postmortem diffusion would aid forensic practitioners in their interpretation of toxicological results. A limitation of previous stomach diffusion studies was the lack of ability to visualise postmortem diffusion in real time, the use of μX-ray Computed Tomography (CT) could overcome this problem. We utilised CT to track the diffusion of the contrast medium caesium ions (Cs⁺) (administered by oral gavage) from the rat stomach over 6 days. We investigated the influence of temperature (4°C and 20°C) and body position (horizontal and vertical). The results show that the a) diffusion of Cs⁺ from the stomach can be visualised over 6 days, over which a significant amount (∼50%) of the diffusion occurs in the first 24h following administration; b) storing the rat at 4°C reduces the distance of diffusion from the stomach by ∼66%; c) body position influences the route of diffusion and d) in 2 of the 16 rats studied Cs⁺ was found in the right lobe of the liver. Overall these results show that CT using Cs⁺ is a good model to visualise postmortem diffusion and that bodies show significant variation in postmortem diffusion. It is also clear that bodies should be refrigerated and postmortem samples should be taken as soon as possible to minimise the influences of postmortem diffusion from the stomach.

Non specific drug distribution in an autopsy case report of fatal caffeine intoxication

Caffeine has long been recognized as an addictive substance that causes autonomic nerve effect, and is known to increase catecholamine secretion from the adrenal glands. In recent years, the risk of ingesting toxic levels of caffeine has increased because of the easy availability of analgesics, CNS (Central Nervous System) stimulant medicine and dietary supplements at shops, health stores and through online purchases. We report the death of a young female resulting from the ingestion for suicide of an online purchased sleepiness-preventing medicine containing caffeine. The autopsy findings included pulmonary edema and congestion plus cutaneous emphysema. The stomach contents included a dark-brown viscous fluid without tablet or food residue. Toxicological examination revealed the presence of caffeine in the right heart blood (154.2 μg/mL) and stomach contents (197.5 μg/mL) (lethal blood level, >80 μg/mL). The highest caffeine content was in the bile (852.3 μg/mL). Biochemical findings showed that catecholamine concentration in the peripheral blood in the iliac vein was elevated. Immunostaining of catecholamine was weak in the adrenal medulla. We recommend highlighting the toxicity risk of ingesting substances with a high caffeine concentration, and we propose that caffeine concentrations should be included in the comprehensive routine forensic toxicological tests for all cases.

Postmortem redistribution of olanzapine following intramuscular administration of olanzapine pamoate in dogs

The potential for postmortem redistribution of olanzapine was investigated in beagle dogs. Olanzapine pamoate monohydrate was administered once every 14 days by intramuscular injection for 3 months to fed male dogs (n=15) at a dose of 20 mg/kg olanzapine (equivalent to 46 mg/kg olanzapine pamoate monohydrate). Blood samples were collected after the fifth (Day 57) and sixth (Day 71) doses to determine olanzapine and N-oxide olanzapine concentrations. On Day 71 at 72 h postdose, dogs were euthanized and placed on their backs without additional manipulation and held for postmortem blood, urine, and tissue collection at room temperature for up to 168 h postdose (96 h after euthanasia). Concentrations of olanzapine and N-oxide olanzapine were determined by liquid chromatography-mass spectroscopy/mass spectroscopy (LC-MS/MS). Postmortem olanzapine concentrations in blood increased up to seven-fold compared to the last quantified antemortem blood concentration. Olanzapine concentrations in vein tissue samples (surrogates for peripheral blood) also increased, whereas other tissue concentrations, such as myocardium, lung, liver, and kidney decreased over the postmortem period. An increase in blood concentration of olanzapine after death was observed in all but one animal, suggesting that postmortem redistribution may occur in dogs following biweekly intramuscular administration of olanzapine pamoate monohydrate. The rise in olanzapine concentrations in blood after death in this study may potentially be attributed to diffusion from multiple tissues to blood and, to a lesser extent, reduction of the N-oxide olanzapine metabolite back to olanzapine. However, the generalizability of these results to humans cannot be confirmed by the present study.

Distribution of enantiomers of methadone and its main metabolite EDDP in human tissues and blood of postmortem cases

Knowledge concerning the distribution of methadone in postmortem human tissue and the effect of postmortem redistribution on methadone is today limited making the choice of a suitable substitute for femoral blood difficult when this is not available. Cardiac blood, femoral blood, muscle, and brain tissue concentrations of the enantiomers of methadone and its metabolite 2-ethyl-1,5-dimethyl-3,3-diphenylpyrrolinium were recorded for 155 postmortem cases. Brain and muscle tissue concentrations exceeded the femoral blood concentrations with a median fold of 2.3 and 1.6, respectively, but both had a better correlation than cardiac blood to femoral blood concentrations. The Kruskal-Wallis test showed a significant dependency on time and body mass index for some of the matrix ratios over femoral blood. We conclude brain or muscle tissue may constitute a better alternative for measurement of methadone than cardiac blood for situations in which femoral blood is not available, despite concentrations in both matrices being systematically higher.

The evaluation of doxepin concentrations in postmortem blood as optional cause of death

The problems concerning an unstable data basis with regard to lethal Doxepin concentrations have been manifested based on a case about a 39-year-old man, who was found dead in his apartment with strangulation marks on his neck, for which a lethal Doxepin intoxication entered the differential diagnosis discussion. For a long time it has been known that postmortem redistribution leads to a falsely inflated concentration as measured in cardiac blood, while the concentrations in peripheral postmortem blood change comparatively little. Despite this, most of the current literature relies on published case report, which fails to mention the location of blood sampling, whereby it is fairly safe to assume that a central sample is intended. Only 9 cases of an isolated lethal Doxepin intoxication have been found, in which the concentrations in blood samples from peripheral vessels had been measured. These values lie between 1.5 and 7.0 mg/L, which is in the lowest quarter of the span of lethal concentrations mentioned in literature without specific mention of the location of the blood sample.

Post-mortem toxicology

Studies examining post-mortem processes are difficult to conduct since changes will have already occurred when the body arrives at the mortuary. While control of collection site for blood can minimize changes in concentration it is very difficult to conduct experiments in humans aimed at understanding the mechanisms and determining the extent of such changes. The use of appropriate animal models can be useful in this regard providing the species and conditions are carefully chosen. Pharmacokinetic studies in humans are also very useful for understanding the changes in drug concentration with time in blood (and other fluids) and also for improving our understanding of drug effects. Unfortunately, doses of illicit drugs that can be given are relatively low to guarantee safety hence extrapolations are made to real life situations. Individual case studies can be useful to describe an unusual or particularly interesting circumstances but little useful information can be obtained when trying to ascertain the role of competing factors, e.g. role of individual drugs when multiple drugs are present, varying toxicity between route of administration, and the role of age or natural disease when drugs are also present. Epidemiological approaches by reviewing large numbers of related cases are the most powerful tool to obtain this information. All of these studies need to operate under the ethical and legal framework appropriate for a jurisdiction. This paper discusses the relative merits of scientific approaches to research in post-mortem toxicology and provides guidance on the most appropriate techniques for future studies.

Post-mortem redistribution of three beta-blockers in the rabbit

To consider the role of the physico-chemical properties of drugs in their post-mortem redistribution, we designed the present study to investigate the influence of lipophilicity using an experimental rabbit model. Three beta-blockers (BB), atenolol, metoprolol and propranolol, with a similar dissociation constant (pK (a)) and increasing partition coefficient (K (p)) were administered intravenously to 18 rabbits. One hour after the last administration, the animals were killed by thiopental injection and placed in a supine position at room temperature. Autopsies were performed at 0, 2, 6, 12, 24 and 48 h post-mortem. Concentrations of the three BB were determined in fluids (right and left cardiac blood, peripheral blood, urine, bile, stomach content, vitreous humour) and tissues (cardiac muscle, lungs, liver, brain, diaphragm, iliopsoas muscle) using a previously published, validated liquid chromatography-electrospray-mass spectrometry method. Our results show that lipophilicity influences post-mortem redistribution of the molecules in a certain number of anatomical sites such as the stomach, lungs, cardiac muscle, cardiac blood or liver, but does not appear to intervene in other sites such as the brain or the vitreous humour.

Vitreous humour as a complementary sample to blood for the detection/confirmation of diazepam: ante-mortem and post-mortem studies in an animal model

The quantification of medical or toxic substances in vitreous humour (VH) could be very useful in forensic toxicology when blood sample determinations are impossible due to absence or deterioration. However, few studies have been made in this area and even fewer have tried to find a relationship between drug levels in both samples. To determine a correlation ratio between blood and VH diazepam (DZ) levels, we performed an experimental study using rabbits administered with a sub-toxic dose of DZ under known and controlled conditions. Blood and VH samples were collected 0.5, 1, 2, 3 and 6 hours after the drug administration in order to determine DZ and its main active metabolite, desmethyldiazepam (DMD). In addition, we have studied an animal group sacrificed 2 hours after intramuscular (i.m.) drug administration with blood and VH collection 24 hours later, to evaluate the existence of possible post-mortem changes. After DZ administration, a fast absorption phase was observed with a plasma Cmax value 1 hour after, followed by a rapid concentration decrease, with a half-life of 1 hour, indicating that, besides elimination, a fast distribution to other organs and tissues and/or hepatic metabolism occurred. Diazepam Cmax value in VH was achieved between 1 and 2 hours, when plasma concentrations had already decreased to half the value. The plasma/VH DZ ratio calculated at this time was 10. In the post-mortem study, while plasma DZ concentration at 24 hours was smaller, DMD levels were higher than those at the time of death. In the VH, both DZ and DMD concentrations at 24 hours were higher than those obtained at the time of death. That is, in both fluids DZ and DMD concentrations were different from those at the time of death and post-mortem distribution and redistribution phenomena occurred. The combination of ante-mortem and post-mortem studies has allowed the determination of a correlation ratio for DZ in the rabbit of 6 x, comparing the concentrations in VH collected 24 hours after death with the concentrations detected in plasma at the time of death. This study opens new perspectives for the use of VH as a complementary sample to blood for DZ detection and confirmation. The putative relevance of the correlation ratio obtained, for forensic toxicology practice with medical substances, namely benzodiazepines, recommends further studies in humans.

Forensic intoxication with clobazam: HPLC/DAD/MSD analysis

Clobazam (Castillium, Urbanil), a benzodiazepine often used as an anxiolytic and in the treatment of epilepsy, is considered a relatively safe drug. The authors present a fatal case with a 49-year-old female, found dead at home. She had been undergoing psychiatric treatment and was a chronic alcoholic. The autopsy findings were unremarkable, except for multivisceral congestion, steatosis and a small piece of a plastic blister pack in the stomach. Bronchopneumonia, bronchitis and bronchiolitis were also diagnosed. Anhigh-performance liquid chromatography (HPLC)/diode array detector (DAD)/mass spectrometry detection (MSD) with electrospray method was developed in order to detect, confirm and quantify clobazam in the post-mortem samples. In the chromatographic separation, a reversed-phase column C18 (2.1 x 150 mm, 3.5 microm) was used with a mobile phase of methanol and water, at a 0.25 ml/min flow rate. Carbonate buffer (pH 10.5) and 20 microl of prazepam (100 microg/ml) as internal standard were added to the samples. A simple and reliable liquid-liquid extraction method for the determination of clobazam in post-mortem samples was described. Calibration curves for clobazam were performed in blood, achieving linearity between 0.01 and 10 microg/ml and a detection limit of 1.0 ng/ml. The clobazam concentration found in post-mortem blood was 3.9 microg/ml, higher than the reported therapeutic concentration (0.1-0.4 microg/ml). The simultaneous acquisition by photodiode array detection and mass spectrometry detection results allowed benzodiazepines to be identified with sufficient certainty. An examination of all the available information suggested that death resulted from respiratory depression due to clobazam toxicity.

Postmortem changes in tissue concentrations of triazolam and diazepam in rats

The aim of this study was to investigate the postmortem changes of concentrations of triazolam and diazepam in the rat model and to confirm the factor causing the phenomenon. We administered triazolam or diazepam orally to rats and then sacrificed them 1 h after administration. Abdominal tissues including stomach content and small intestine, thigh muscle and heart blood were collected at 0, 12, 24 h after death, and postmortem changes of the two drug concentrations were compared. Drug concentrations in the samples were analyzed by a selected ion monitoring of gas chromatography/mass spectrometry. Gastrointestinal postmortem concentrations of triazolam and diazepam decreased. On the other hand, the drug concentrations in the liver and kidney increased markedly, and those in lung and heart blood increased slightly during postmortem periods by diffusion from the gastrointestinal tract. The patterns of both drug concentration changes were similar. However, the extent of the triazolam increase tended to be larger than that of diazepam. This difference may be accounted for by lower triazolam concentrations before death. The postmortem drug concentrations of thigh muscle did not change when administered with triazolam and diazepam. For both triazolam and diazepam, a significant correlation was observed in the drug concentration between the small intestine and the kidney at 24 h after death, indicating that major cause of the change in the drug concentration in the kidney was diffusion from the small intestine up to 24 h after death. The results in this study indicate that diazepam as well as triazolam diffuses from the gastrointestinal tract into the surrounding tissues after death and suggest that the diffusion is influenced by their pharmaceutical properties before death.

Effect of post-mortem changes on peripheral and central whole blood and tissue clozapine and norclozapine concentrations in the domestic pig (Sus scrofa)

Interpretation of the results of psychoactive or other drug measurements in post-mortem blood specimens may not be straightforward, in part because analyte concentrations in blood may change after death. There is also the issue of comparability of plasma (or serum) results to those obtained in whole blood. To investigate these problems with respect to clozapine, this drug (10mg/kg daily) was given orally to two pigs. Blood was collected 3h post-dose on day 7, the animals were sacrificed, and blood taken from central and peripheral veins for up to 48 h after death. Tissue samples were also collected immediately after death and at 48 h. Ante-mortem whole blood clozapine/N-desmethylclozapine (norclozapine) concentrations were 0.86/1.07 and 1.11/1.15 mg/l in pigs 1 and 2, respectively. Blood clozapine and norclozapine concentrations generally increased after death (central vein: clozapine up to 300%, norclozapine up to 460%; peripheral vein: clozapine up to 155%, norclozapine up to 185%). Initial blood and kidney clozapine and norclozapine concentrations were comparable in both animals, but were some two-fold higher in heart, liver and striated muscle in pig 2. In both animals, the heart and striated muscle clozapine and norclozapine concentrations had increased some two- to three-fold at 48 h, whilst the liver and kidney concentrations were essentially unchanged. The reason for the increase in heart and striated muscle concentrations at 48 h is unclear, but could be simple variation in sample site. The plasma:whole blood distribution of clozapine and norclozapine was studied in vitro. In human blood (one volunteer donor, haematocrit 0.50) the plots of plasma versus whole blood concentration were linear for both analytes across the range 0.1-1.5mg/l, although clozapine favoured plasma (plasma:whole blood ratio=1.12), whereas norclozapine favoured whole blood (ratio 0.68). In pig blood, the plots of plasma versus whole blood were non-linear in both cases, although clozapine favoured plasma to a greater extent than norclozapine. This may be due to lower plasma clozapine and norclozapine protein binding capacity in the pig as compared to man.

Estimating antemortem drug concentrations from postmortem blood samples: the influence of postmortem redistribution

AIMS

To compare blood drug concentrations during life with postmortem drug concentrations measured from a peripheral site and a central site.

METHODS

Coroner's cases from October 1990 to July 1997 were reviewed. Six cases had data on both antemortem and postmortem blood drug concentrations. The postmortem to antemortem ratio was compared with the postmortem central to peripheral ratio, using cardiac blood as a central site and femoral blood as a peripheral site.

RESULTS

Drugs that have a high postmortem central to peripheral ratio; that is, drugs that exhibit considerable postmortem redistribution, also have high postmortem to antemortem ratios.

CONCLUSIONS

A large degree of error can arise from attempting to estimate antemortem drug concentrations and the ingested dose from postmortem measurements. The chosen site and technique for postmortem blood sampling can greatly influence the concentration of drug measured.

In vitro approaches to predicting drug interactions in vivo

In vitro metabolic models using human liver microsomes can be applied to quantitative prediction of in vivo drug interactions caused by reversible inhibition of metabolism. One approach utilizes in vitro Ki, values together with in vivo values of inhibitor concentration to forecast in vivo decrements of clearance caused by coadministration of inhibitor. A critical limitation is the lack of a general scheme for assigning intrahepatic exposure of enzyme to inhibitor or substrate based only on plasma concentration; however, the assumption that plasma protein binding necessarily restricts hepatic uptake is not tenable. Other potential limitations include: flow-dependent hepatic clearance, "mechanism-based" chemical inhibition, concurrent induction, or a major contribution of gastrointestinal P450-3A isoforms to presystemic extraction. Nonetheless, the model to date has provided reasonably accurate forecasts of in vivo inhibition of clearance of several substrates (desipramine, terfenadine, triazolam, alprazolam, midazolam) by coadministration of selective serotonin reuptake-inhibitor antidepressants and azole antifungal agents. Such predictive models deserve further evaluation, since they may ultimately yield more cost-effective and expeditious screening for drug interactions, with reduced human drug exposure and risk.

Postmortem diffusion of drugs from gastric residue: an experimental study

Postmortem drug diffusion from gastric residue was assessed in a human cadaver model. Fifty milligrams of amitriptyline (Ami) and 5 g of paracetamol (Par) suspended in 350 ml of 10% methanol, 0.1 N HCl, and 50 ml urograffin with 5 g lithium carbonate (alkaline model) or without lithium (acidic model) was instilled into the stomach through an esophageal tube via a neck dissection. Multiple samples were obtained after 48 h at room temperature (range in mean hourly room temperature: 15.6-20.7 degrees C, n = 9). The pH of the gastric contents (alkaline model range = 8.3-8.9, n = 5; acidic model range = 3.4-3.8, n = 5) had no significant effect. Drug diffusion was most marked in the left lung base, with drug concentrations (micrograms/g) of 0.1-13.9 for Ami, 65-524 for Par, and 13-161 for lithium. Similarly affected were the left lobe of the liver (Ami, 0.1-54.9; Par, 7-218; lithium, 7-39), the spleen (Ami, 0.6-24.3; Par, 104-663; lithium, 27-106), and pericardial fluid (Ami, 0-4.5; Par, 48-641; lithium, 12-56). Diffusion into gallbladder bile, cardiac blood, aortic blood, and blood of the inferior vena cava was less severe. The left kidney and left lung were more severely affected than the right kidney and lung, and similarly the left and right psoas muscles. Least affected was the right anterior lobe of the liver and the lung apexes. This phenomenon may significantly influence drug concentrations in liver and in blood samples obtained from the torso, and consequently liver/blood drug ratios. To circumvent the problem of postmortem drug diffusion from the stomach, it is recommended that blood be sampled from a peripheral vessel, skeletal muscle from a limb, liver from deep within the right lobe, and lung from the apex rather than the base.

Experimental studies on postmortem diffusion of ethanol-d6 using rats

In an investigation of postmortem ethanol diffusion deuterium-labeled ethanol-d6 was instilled by peroral gavage immediately after death by CO into the stomach of rat carcasses which were subsequently kept for 12-72 h at 5 or 30 degrees C. The heart blood, abdominal fluid and several tissues were collected and analyzed by head space gas chromatography-mass spectrometry. Rat carcasses showed no macroscopic changes until at least 72 h at 5 degrees C, and 12 h at 30 degrees C. At 30 degrees C, slight macroscopic change was observed after 24 h, moderate change after 48 h and marked change after 72 h. In the abdomen ethanol-d6 diffused gradually into neighboring organs (hepatic left lobe, left kidney and spleen) at 5 degrees C, with ethanol-d6 reaching a peak concentration of 0.75-2.38 mg/g at 24 h. At 30 degrees C, ethanol-d6 was also detected in neighboring organs and reached a peak concentration of 1.06-2.61 mg/g at 12 h. Thereafter, the ethanol-d6 concentration in the liver, kidney and spleen decreased, with concentrations ranging from 0.30 to 0.61 mg/g at 30 degrees C and 0.05 to 1.47 mg/g at 5 degrees C at 48 h. In the femoral skeletal muscle, ethanol-d6 was not detected until 24 h or more storage at 30 degrees C and never detected at 5 degrees C. In the brain and the organs in the thoracic cavity ethanol-d6 was detected after 12 h or more at 5 or 30 degrees C. Comparison of these results of direct peroral gastric instillation with those when ethanol-d6 was injected into the stomach through a laparotomy incision suggest that the brain and thoracic cavity changes were a result of diffusion from the mouth and esophagus. After 24 h at 30 degrees C, the postmortem ethanol production (0.33-0.85 mg/g) was comparable to those in previous reports. These results indicate that the assessment of ethanol concentration in the heart blood and organs in autopsy cases must be carefully conducted in comparison with the alcohol content of the stomach.

Zopiclone poisoning: tissue distribution and potential for postmortem diffusion

Zopiclone is the first cyclopyrrolone hypnotic and is chemically unrelated to any existing drug. The authors studied the tissue distribution and postmortem redistribution of zopiclone in a fatal suicidal overdose. A 29-year-old female weighing 64 kg had cardiac blood ethanol 153 mg% and zopiclone blood concentrations in the range 0.9-2.0 microgram/ml in 10 distinct sampling sites. After 40 h at room temperature the range was 0.9-1.8 micrograms/ml in 15 samples. Portal venous blood and urine concentrations were 3.0 and 10.5 micrograms/ml, respectively. Tissue concentrations (microgram/g) were spleen 5.8, peri-renal fat 5.0, psoas muscle 3.3, brainstem 2.8, gastrocnemius muscle 1.9, myocardium 1.6, and kidney 1.7. Eight liver samples had concentrations in the range 0.5-4.9 micrograms/g, with highest concentrations in the left lobe and adjacent to the gallbladder, probably reflecting postmortem diffusion from gastric residue (700 ml, 55.1 micrograms/ml) and bile (14.1 micrograms/ml). Of six lung samples, paired upper and middle samples had concentrations in the range 2.1-2.3 micrograms/g, the right postero-basal 1.3 micrograms/g and the left postero-basal 3.4 micrograms/g. Drug concentration in putrefactive pleural fluid was also higher on the left (2.1 micrograms/ml) than the right (1.4 micrograms/ml), probably reflecting postmortem diffusion from gastric residue. The authors conclude that zopiclone showed little preferential concentration in solid organs and consequently has relatively stable postmortem blood concentrations, with little drug redistribution artefacts. Postmortem diffusion from gastric drug residue elevates drug levels in the left lobe of the liver and left lung lower lobe.

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 CO2 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 mumol/kg at 0.1 h to 49.1 +/- 7.8 mumol/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.(ABSTRACT TRUNCATED AT 250 WORDS)