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Postmortem Redistribution
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Until recently, the established approach to the interpretation of postmortem drug concentrations was thought to be a simple process. The concentration of a drug and/or metabolite, measured at autopsy, was static and could be simply compared to established therapeutic and/or toxic concentration ranges in living subjects. This simplistic approach has been proven to be wrong. The postmortem concentrations of drugs have been demonstrated to exhibit a site (anatomical) dependency [1]. Heart blood drug concentrations for many drugs are usually greater than the measured concentrations from peripheral sites; such as femoral veins. To further complicate the matter, the concentrations of drugs in postmortem specimens frequently increase with the increasing postmortem interval. The change in the peripheral specimens appears to be of less magnitude and at a slower rate than that of heart blood drug concentrations. There are energy-dependent processes that maintain drug concentration gradients during life, after death these processes cease and changes in the gradient are expected to occur. Drugs will undergo diffusion down concentration gradients. Drugs in high concentrations in various tissue reservoirs; such as liver, lung, and heart will be separated from these protein bound sites and passively diffuse into adjacent tissue and central blood vasculature [2]. Another reservoir with orally ingested drugs is the stomach [3] with diffusion into the lower lobe of the left lung and left lower lobe of the liver and into the heart tissues. This process has been termed postmortem diffusion or postmortem redistribution (PMR). The term PMR was used by Koren and MacLeod in the title of their 1985 [4] paper on changes in digoxin concentration after death in a rat. However, long before the prodigious work of Prouty and Anderson [1], there were observations and reports in the literature, decades before, of these anatomical site differences in blood drug concentrations. Curry and Sunshine [5] reported
Postmortem Toxicology. DOI: https://doi.org/10.1016/B978-0-12-815163-1.00013-7 © 2019 Elsevier Inc. All rights reserved.
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large differences in barbiturate concentrations in central blood samples as compared to a peripheral sample. They were one of the first to suggest the utilization of peripheral blood sample and suggest that further research in this area of postmortem toxicology was needed. Gee et al. [6] corroborated Curry and Sunshine’s data. They too gave a cautionary note that the area/ site of collection is an important consideration for interpretation. Holt and Benstead [7] made the observation that three different postmortem samples collected from three different anatomical sites in the same body contained different concentrations of digoxin and speculated that the drug may have been redistributed in the body after death. Vorphal and Coe [8] compared ante- and postmortem digoxin concentrations in 27 subjects. They observed that the postmortem digoxin concentrations were higher than the antemortem concentrations. They also noted differences in the postmortem samples collected; heart, femoral, and subclavian blood samples and that the heart blood samples had the highest concentration of digoxin. They concluded that this was a “special case” in that digoxin is highly bound to the myocardium and that the drug probably diffused from the cardiac tissue into the heart blood. The body of knowledge evolving around PMR of drugs began to demonstrate that the redistribution depended on many factors; the two predominate ones were the anatomical site of the blood collection and the postmortem interval. Brandt [9] presented data at the American Academy of Forensic Sciences involving tricyclic antidepressants (TCAs). The study concluded that the concentration of TCAs was a function of the anatomical site of collection and the length of the postmortem interval. One of the sentinel cases which brought the phenomena of PMR to the forefront of the scientific community occurred in 1987 (Rohrig—Personal Communication and [10]). A 63-yearold female hospitalized in a state facility died overnight. At autopsy, the only anatomically significant finding was a large brain tumor, of a size and location that would explain the woman’s death. Routine toxicology was performed and desipramine, which was prescribed, was detected. However, the heart blood concentration was 6.3 mg/L, and in a range that could be considered lethal. Since the care providers were in control of the decedent’s medication, an extensive investigation was undertaken; including a careful review of pharmacy records, which did not reveal overdispensing. A standard pharmacokinetic equation [Dose 5 weight (kg) 3 volume of distribution (L/kg) 3 blood concentration (mg/L)] suggested a large amount
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of drug was ingested (estimated dose: 6600 mg or 264 25 mg tablets); which exceed the available stock of desipramine. The case suggested that the postmortem blood concentration may not necessarily reflect the antemortem concentration of the drug. This finding prompted an extensive study covering a wide variety of drugs (n 5 45) and the impact of the anatomical site of collection and the postmortem interval [1]. Their study involved collection of a heart blood sample, via a cardiac stick, that was sent with the body to the morgue. At autopsy additional specimens were collected; heart blood, femoral blood, as well as other biological fluids and tissues. The authors concluded that the drug concentration of weakly basic drugs had a tendency to increase with the postmortem interval and that the central blood concentrations tend to be greater than the peripheral blood drug concentrations. They also noted that the drug concentration in the peripheral samples also increased over the postmortem interval. They further cautioned that calculation of dose from a heart blood sample should be avoided. In addition to drugs passively moving down a concentration gradient; from high concentration in tissue into surrounding blood supply other factors will influence drug redistribution. These authors and others [2,11 14] have concluded that the chemical characteristics of the drug also play a major role in the propensity to undergo PMR. Drugs with a high volume of distribution (Vd . 3 L/kg), weakly basic in chemical nature (pKa . 7) and have a high octanol:water coefficient; that is, are highly lipophilic and make the drug more likely to redistribute. The longer the postmortem interval, the more likely there will be an increase in concentration for drugs that exhibit PMR. Muscle rigor and putrefactive gas build-up, due to decomposition, can compress peripheral vasculature and may cause postmortem circulation of blood and potentially alter the drug distribution. Jones and Pounder [15] illustrate in a case study of one decedent that not all drugs will exhibit same anatomical site differences in concentration. The blood concentrations of imipramine and its metabolite desipramine in central blood vessels were 50% 760% higher as compared to concentrations the in peripheral vasculature. The site to site variation of diphenhydramine and codeine were much less dramatic, ranging from 2.5 to 6 times higher in the pulmonary vein as compared to the subclavian vasculature. However, the blood concentrations for acetaminophen and ethyl alcohol exhibited little variation from site to site. The author presented additional case study data that
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demonstrate substantial site differences in blood drug concentrations for some but not all drugs [16]. Prouty and Anderson [17] confirmed the insignificant variation in heart blood to femoral blood ethyl alcohol concentrations. In the cases that did vary more than 0.02 g%, the specimens had unique characteristics; significant differences in physical appearance, trauma to the area of collection, gross differences in hematocrit, or large volume differences in the two specimens collected. A heart blood to femoral blood (HB:FB) or central blood to peripheral blood (C:P) ratios are considered good indicators of a drug with the probability to undergo PMR; the higher the ratio the more likely the drug will undergo redistribution [18,19]. A drug with a high C:P ratio is thought to have the propensity to undergo substantial redistribution after death. However, a low C:P ratio (less than unity) does not necessarily indicate the drug will not undergo redistribution. Dalpe-Scott et al. [20] published the C:P ratio for 113 drugs from 320 postmortem cases. The central blood concentration was higher in most cases the C:P ratio ranged from greater than 1 up to 21 times higher diphenhydramine was the highest at 21-fold. However, six drugs had ratios # 1; ephedrine, hydrocodone, hydroxyzine, metoprolol, procyclidine, and trifluroperazine that would be expected to undergo some redistribution. There have been other reports of drugs with C:P ratios of .1, which would not be expected to undergo redistribution; for example, salicylic acid [18], carisoprodol [21], and tramadol [22]. McIntyre and Escott [23] have proposed a liver to peripheral blood (L:P) ratio as a new marker for PMR. They suggest that a ratio exceeding 20 is indicative of the drug undergoing redistribution, where a ratio of less than 5 indicating no propensity to undergo redistribution. In more recent papers, McIntyre [24 26] proposes the concept of a PMR factor (F), in which he characterizes as having a direct relationship to the corresponding antemortem concentration of the drug. The mathematical relationship suggested is AM (antemortem concentration) 5 P (peripheral postmortem concentration)/F (PMR factor or L:P ratio). However at this point, there is minimal data to support the validity of this concept; McIntyre does suggest further work needs to be undertaken to support this hypothesis. In addition to the chemical nature of the drug, the anatomical site blood is drawn from has an influence due to the anatomy. The vast majority of studies have come to the conclusion that the various factors influencing the PMR of drugs include: the condition of the body; the physical barriers—decomposition
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and/or trauma, allowing for microbial invasion, residual enzymatic activity, the pH of tissues, and the postmortem movement of blood due to putrefaction, rigor mortis, and gravitydependent blood flow. Peripheral blood samples are generally collected from the femoral vein. These veins are a preferred anatomical site due to the larger number of values in the femoral vein as compared to the vasculature as it becomes more central. The valves in the veins tend to restrict the postmortem movement of blood and passive diffusion of the drug through the vasculature. There have been more recent observations that “milking” of the veins to get a larger blood sample will overcome the physical barrier provided by the values and the drug concentrations in these “milked” samples tend to be more reflective of a central specimen. Some practitioners have suggested that “Clamping” the femoral vein prior to collection will prevent contamination from more central sources such as iliac vessels or the inferior vena cava. Hargrove and McCutcheon [27] undertook a study to determine whether or not a “blind stick” femoral blood samples were significantly different from blood collected from cut-down clamped femoral vessels. They evaluated eight different drugs representing four different drug classes. There were three serotonin-reuptake inhibitors: sertraline, paroxetine, and citalopram; two different benzodiazepines: diazepam and alprazolam; two antihistamines: diphenhydramine and promethazine, and one opiate: hydrocodone. The authors found that the clamped femoral blood concentrations and the blind stick concentrations were found to be in good agreement. All four drug classes had a ratio of approximately 1.0. They concluded that the “style” of collection of the peripheral blood sample did not have a significant impact on the resulting femoral blood drug concentrations. Lemaire et al. [28] investigated the impact on drug concentrations of blind stick and dissection/clamping blood collection techniques for sampling of subclavian and femoral sites. They evaluated the impact of the collection techniques on three drugs; diazepam, methadone, and morphine. The blood concentrations of diazepam and methadone were lower with the blind stick as compared to the dissected/clamped vessel for both the subclavian and femoral veins. This is in conflict with what Hargrove and McCutcheon found for diazepam in femoral sample; that there was no significant difference in concentration between the two techniques utilized for blood collection. Morphine concentrations in Lemaire et al. [29] study were lower from the subclavian site with the dissection and clamping technique, as compared to a blind stick; whereas with the blind
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stick technique, the morphine concentrations were lower at the femoral site as compared to collection by dissection/clamping of the vessel. Hargrove and Molina [30] did not observe any significant variation in morphine concentration from blood collected from the femoral vessel, regardless of collection techniques; blind stick or dissection/clamping. Although the variation will effect the calculation of a C:P ratio, the differences should not grossly impact in a negative manner the interpretation of the drug result. A fair amount of postmortem toxicological analyses are performed offsite at a reference laboratory. McLemore et al. [31] investigated the effects of transport conditions on the collected blood samples. They examined three different blood specimen/ shipping procedures to evaluate the impact on drug concentrations. The authors collected femoral blood via a “blind stick” in the inguinal area of the body and shipped to the laboratory at ambient temperature. A second “blind stick” in the same area was performed and the collected femoral blood was shipped to the laboratory on dry ice. An iliac blood sample was obtained on the opposite side by direct visualization and clamping the vessel prior to blood collection. This sample was shipped to the laboratory on dry ice. The total number of autopsy cases evaluated was 112, with 78 different drug or drug metabolites detected. The authors did not find any statistical difference between the three collection/shipping methods. However, in 49 of the cases, the “blind stick” femoral sample shipped at ambient temperature was positive, while the iliac, “blind stick” femoral shipped on dry ice or both were negative. The drug or drug metabolite in which this occurred in multiple cases was delta9-tetrahydrocannabinol, sertraline/norsertraline and fluoxetine/ norfluoxetine, and hydromorphone; and multiple other analytes in one or two cases. The authors suggest that analyte instability due to the freeze/thaw cycle may be the reason for the negative results. Peripheral blood samples are preferred for quantitative analyses in that they will more closely reflect the antemortem concentration. A more recent study by Gerostamoulos et al. [32] evaluated a large number of drugs (n 5 52) and the impact of the postmortem interval. Their study compared “admission” blood (antemortem) to femoral autopsy blood drug concentrations. The postmortem interval ranged up to 164 hours (6.4 days), with a mean value of 64 hours. They found that more than 45% of the drugs had a change in concentration that was greater than or equal to 10%. The selective serotonin-reuptake inhibitors (venlafaxine, mirtazapine, and paroxetine) had
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average increases of approximately 30% irrespective of the postmortem interval. Their overall conclusion was that there may be a rise in femoral blood drug concentration irrespective of the postmortem interval. McIntyre et al. [33] made similar observations with methamphetamine and amphetamine, albeit with a small sample size (n 5 3 and 2, respectively). The antemortem samples were drawn between 7 and 22 minutes prior to pronouncement of death and the postmortem interval ranged from 5.25 to 30.5 hours. The peripheral to antemortem blood ratios averaged 1.51 and 1.50 for methamphetamine and amphetamine, respectively. In a study looking at the PMR of fentanyl, Olsen et al. [34] evaluated seven cases in which femoral blood was collected at two intervals; shortly after death and at autopsy. The mean collection times were 4.0 and 21.6 hours following death, respectively. All samples demonstrated a rise in fentanyl concentration between the two collection time, however, the rate of rise varied dramatically between the cases; minimal change in concentration, 5.0 5.1 µg/L to a dramatic change in concentration of 4.7 52.5 µg/L. PMR is site dependent with drug diffusing from tissue depots with high drug concentrations into the blood compartment; the central (Heart) blood compartment being the most effected. However, Moriya and Hashimoto [35] described a case where the femoral drug blood concentrations were presumably increased due to diffusion of the drug from the bladder. They reported a case of a 16-year-old male who was found dead in a stream. The decedent had a history of OTC (over-the-counter) drug abuse. Autopsy did not reveal an anatomical cause of death; one significant finding was that the bladder contained 600 mL of urine. The cause of death was certified as “Drowning after OTC drug abuse.” The concentration of diphenhydramine and dihydrocodeine was higher in the femoral blood as compared to the heart blood drug concentrations. They hypothesized that during the comatose period, a large volume of urine collected containing high concentrations of the drugs. The drugs then diffused from the bladder into the femoral blood compartment. Femoral blood specimens are routinely used for quantitative analyses to minimize the impact of PMR. However as noted by Prouty and Anderson [1] and others, they have demonstrated that there may still be an increase in femoral blood drug concentration over the postmortem interval. To address the challenge of PMR, many researchers have evaluated alternate specimens to assist in the interpretation of a case. These alternate specimens are remote to the “central” part of the body,
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and therefore would be resistant to passive diffusion of a drug from the high concentration depots. These alternative specimens include popliteal blood samples, which are distal to a femoral blood sample, vitreous fluid, brain tissue, and new areas of investigation include cerebral spinal fluid, intraosseous fluid (IOF), and synovial fluid. Lemaire et al. [29] has proposed that popliteal vein blood is less prone to PMR as compared to FB. This is thought to be because the popliteal vein is more distal site to the central body, as compared to the femoral vein. To sample the blood, given the deep anatomical location in the leg, the dissection was necessary to access the vein; the vessel was then clamped prior to collection, to prevent admixture of blood in the femoral vein. The authors evaluated 30 autopsy cases containing one or more of the following drugs; diazepam, methadone, and morphine. They concluded that blood sampled from this anatomical site was less prone to PMR as compared to FB. There appears to be no significant difference between left and right popliteal blood samples [28]. In a later study [36], they evaluated the impact of PMR on the same drugs, in 57 autopsy cases, over time. The authors conclude that blood from the popliteal vein was less prone to PMR as compared to blood from other anatomical sites, including FB. Vitreous humor has been looked as an alternative matrix for postmortem toxicology over the last five decades [37]. Sturner and Garriott [38] examined blood and vitreous in 56 cases of decedents dying from drug overdose and other causes. The challenges early on were the small sample size available and the sensitivity of the analytical procedures. However, with the advent of immunoassay techniques [39,40], (high-performance liquid chromatography [41] and gas chromatography mass spectrometry [42]), these challenges no longer existed and more research was conducted on comparing vitreous drug concentrations to paired blood concentrations. De Letter et al. [43] in a rabbit dosing study gave IV 3,4-methylenedioxymethamphetamine (MDMA) to rabbits and compared the antemortem blood concentration to the vitreous humor concentration in animals held at room temperature. The postmortem MDMA concentrations in the vitreous were closer to the antemortem blood concentrations than the postmortem cardiac blood. The authors suggest that this preliminary animal study indicated that vitreous humor may be a viable sample to address the challenges of PMR and predict the antemortem drug concentration. Be´valot et al. [44] conducted a review of using vitreous humor as a matrix for the detection of drugs in
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postmortem cases. The authors suggest that vitreous humor has several advantages in forensic toxicology; it is less prone to PMR, it is easy to collect, has few interfering substances in the analytical analyses, and is stable over the postmortem interval. The authors provide an extensive table presenting blood concentrations (cardiac and peripheral) and vitreous humor concentrations for a variety of drugs. They suggest further investigation is needed to fully assess the viability of this sample as a tool to better predict the antemortem blood concentration in the decedent. Kennedy [45] added to this body of knowledge in her Master’s thesis. The author investigated the distribution of diphenhydramine, tramadol, and methadone in vitreous humor, blood (heart blood and femoral), and brain tissue. The conclusion from the study was that the average correlation ratios showed diphenhydramine and methadone were found in higher concentrations in blood (heart and femoral) and brain as compared to vitreous humor. Whereas, the average correlation ratio for tramadol was found higher in the vitreous than in blood, with nearly equal concentrations in vitreous humor and brain. Additional data are needed to fully assess the viability of this specimen in it utility to address the challenges of PMR. Brain tissue may be a valuable specimen in assisting in the interpretation of postmortem toxicological results. The protected and isolated position of the brain may eliminate the challenges of PMR and delay or attenuate residual enzymatic activity on some compounds which may artificially lower their concentration. The tissue is more immune to decomposition allowing for the detection and quantitation in the tissue as compared to cavity fluid or organ tissue within the thoracic/ abdominal cavity. However, there are a limited amount of data comparing brain drug concentrations to blood concentration, specifically femoral blood concentrations. Baselt [46] has some brain data in individual monographs; however, there is a paucity of data as to the quantitative distribution of drugs in the brain. Rohrig and Hicks [47] presented data from heart, femoral blood, and brain tissue for 30 drugs and drug metabolites in cases submitted for autopsy examination. The authors found a positive correlation between blood concentrations to brain concentrations. However, this study did not breakout brain concentrations found in cases where the drug was the direct cause of death or contributory versus noncontributory to the death. There are a limited number of studies that provide a breakdown of brain concentrations where the role of the drug in the death was delineated along with the brain concentration. These
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studies provide postmortem reference ranges in blood and brain tissue, thus minimizing the impact of PMR; quetiapine [48], nitrobenzodiazepines [49], alprazolam, bromazepam, chlordiazepoxide, diazepam, and their metabolites [50] and citalopram, duloxetine, mirtazapine, and sertraline [51]. There are some emerging data for drug analyses in bone marrow aspirates or IOF and their utility to be somewhat resistant to PMR. Tominaga et al. [52] evaluated bone marrow aspirate as a substitute of blood as a proposed specimen when blood was not available. They opined that aspirate bone marrow samples contained a large amount of peripheral blood, and therefore would be a suitable alternative substitute and may be useful in addressing PMR. IOF (bone marrow aspirate) has recently been investigated as an alternative specimen for toxicological analyses that is immune from PMR, due to its isolation from surround tissue. IOF was collected from right and left tibias and humerus of 29 decedents, along with routine autopsy samples [53]. Both specimens were screened with immunoassay for amphetamines, benzodiazepines, cannabinoids, cocaine, fentanyl analogs, methadone, methamphetamine, opioids, oxycodone, phencyclidine, and TCAs. There was a strong correlation between the screen result in both cardiac blood and IOF; ranging from a low of 63% to 100%, with the majority having a 100% correlation. Methamphetamine, amphetamine, and tetrahydrocannabinol positive screen results were confirmed in blood, using gas chromatography mass spectrometry; there too existed a strong positive correlation of 100%. The author also did not observe any site differences in the qualitative screen result; that is, right, left tibia, and humerus IOF. They go on to suggest that not only being a possible matrix for mitigating the impact of PMR, they further opine that IOF may be potentially less-compromised tissue in decomposed and/or traumatized bodies and that further study is needed. In addition to a drug undergoing PMR, there may be other confounding factors that influence site dependency of drug concentrations. Acute drug exposure from an accidental or suicidal overdose causing death may result in an incomplete distribution of the drug throughout the body. Baud et al. [54] evaluated 24 patients who present in a comatose state due to an acute amitriptyline overdose. The author measured amitriptyline concentrations in paired femoral arterial and venous blood samples, finding significant different concentrations. Sato et al. [55] found similar results in paired femoral arterial and venous blood samples in 35 patients who were admitted to the hospital for an acute meprobamate overdose.
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Residual enzymatic activity may alter drug concentrations. The enzymes may be endogenous; residual tissue enzymatic activity, gut microflora possessing enzymatic activity and released during the putrefactive process or traumatic injury or bacterial enzymatic activity may also be introduced by penetrating trauma. Robertson and Drummer [56] found various nitrobenzodiazepines were metabolized “postmortem” by a variety of bacteria which possessed nitroreductase enzymes; metabolizing the nitrobenzodiazepine to their respective 7-amino metabolite.
References [1] Prouty RW, Anderson WH. The forensic science implications of site and temporal influences on postmortem blood-drug concentrations. J Forensic Sci 1990;35:243 70. [2] Pe´lissier-Alicot A, Gaulier J, Champsaur P, Marquet P. Mechanisms underlying postmortem redistribution of drugs: a review. J Anal Toxicol 2003;27:533 43. [3] Pounder DJ, Fuke C, Cox DE, Smith D, Kuroda N. Postmortem diffusion of drugs from gastric residue. Am J Forensic Med Pathol 1996;17:1 7. [4] Koren G, MacLeod SM. Postmortem redistribution of digoxin in rats. J Forensic Sci 1985;30:92 6. [5] Curry AS, Sunshine I. The liver:blood ratio in cases of barbiturate poisoning. Tox Appl Pharmacol 1960;2:602 6. [6] Gee DJ, Dalley RA, Green MA, Perkins MA. Postmortem diagnosis of barbiturate poisoning. In: Ballantyne B, editor. Forensic toxicology. Bristol: John Wright and Sons; 1974. p. 37 51. [7] Holt DW, Benstead JG. Postmortem assay of digoxin by radioimmunoassay. J Clin Pathol 1975;28:483 6. [8] Vorphal TE, Coe JI. Correlation of antemortem and postmortem digoxin levels. J Forensic Sci 1978;23:329 34. [9] Brandt C. Postmortem changes in serum levels of the tricyclic antidepressants. In: Presented at the annual meeting of the American Academy of Forensic Sciences. Los Angeles CA, 1981. [10] Anderson B. Postmortem interpretation 2 - Postmortem redistribution of drugs. “Postmortem toxicology: from autopsy to interpretation” (SOFT Continuing Education Committee Workshop) Presented at the annual meeting of the Society of Forensic Toxicologists. Atlanta GA 2015. [11] Ferner RE. Post-mortem clinical pharmacology. Br J Clin Pharmacol 2008;66:430 43. [12] Han E, Kim E, Hong H, Jeong S, Kim J, In S, et al. Evaluation of postmortem redistribution phenomena for commonly encountered drugs. Forensic Sci Int 2012;219:265 71. [13] Yarema MC, Becker CE. Key concepts in postmortem drug redistribution. Clin Toxicol (Phila) 2005;43:235 41. [14] Zilg B, Thelander G, Giebe B, Druid H. Postmortem blood sampling comparison of drug concentrations at different sites. Forensic Sci Int 2017;278:296 303. [15] Jones GR, Pounder DJ. Site dependence of drug concentrations in postmortem blood a case study. J Anal Toxicol 1987;11:186 90.
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[16] Pounder DJ, Jones GR. Post-mortem drug redistribution a toxicological nightmare. Forensic Sci Int 1990;45:253 63. [17] Prouty RW, Anderson WH. A comparison of postmortem heart blood and femoral blood ethyl alcohol concentrations. J Anal Toxicol 1987;11:191 7. [18] Cook DS, Braithwaite RA, Hale KA. Estimating antemortem drug concentrations from postmortem blood samples: the influence of postmortem redistribution. J Clin Pathol 2000;53:282 5. [19] Kennedy M. Interpreting postmortem drug analysis and redistribution in determining cause of death: a review. Path Lab Med Int 2015;7:55 62. [20] Dalpe-Scott M, Degouffe M, Garbutt D, Drost M. A comparison of drug concentrations in postmortem cardiac and peripheral blood in 320 cases. Can Soc Forensic Sci J 1995;28:113 21. [21] McIntyre IM, Sherrard J, Lucas J. Postmortem carisoprodol and meprobamate concentrations in blood and liver: lack of significant redistribution. J Anal Toxicol 2012;36:177 81. [22] Costa I, Oliveira A, de Pinho PG, Teixeira HM, Moreira R, Carvalho F, et al. Postmortem redistribution of tramadol and O-desmethyltramadol. J Anal Toxicol 2013;37:670 5. [23] McIntyre IM, Escott CM. Postmortem drug redistribution. J Forensic Res 2012;3:e108. Available from: https://doi.org/10.4172/2157-7145.1000e108. [24] McIntyre IM. Identification of a postmortem redistribution factor (F) for forensic toxicology. J Anal Sci Tech 2014;5:24. Available from: https://doi. org/10.1186/s40543-014-0024-3. [25] McIntyre IM. A theoretical postmortem redistribution factor (Ft) as a marker of postmortem redistribution. Eur J Forensic Sci 2015;2:24 6. [26] McIntyre IM. Analytical data supporting the “theoretical” postmortem redistribution factor (Ft): a new model to evaluate postmortem redistribution. Forensic Sci Res 2016;1:33 7. [27] Hargrove VM, McCutcheon JR. Comparison of drug concentrations taken from clamped and unclamped femoral vessels. J Anal Toxicol 2008;32:621 5. [28] Lemaire E, Schmidt C, Denooz R, Charlier C, Boxho P. Postmortem concentration and redistribution of diazepam, methadone, and morphine with subclavian and femoral vein dissection/clamping. J Forensic Sci 2016;61:1596 603. [29] Lemaire E, Schmidt C, Denooz R, Charlier C, Boxho P. Popliteal vein sampling and the postmortem redistribution of diazepam, methadone, and morphine. J Forensic Sci 2016;61:1017 28. [30] Hargrove VM, Molina DK. Peripheral postmortem redistribution of morphine. Am J Forensic Med Pathol 2014;35:106 8. [31] McLemore J, Schwilke E, Shanks K, Klein D. The effects of acquisition of blood specimens on drug levels and the effects of transportation conditions on degradation of drugs. DOJ Final Technical Report, NIJ Award #2010-DNBX-K216. 2013; document number 244230. [32] Gerostamoulos D, Beyer J, Staikos V, Tayler P, Drummer O. The effect of the postmortem interval on the redistribution of 52 drugs: a comparison of admission and autopsy blood specimens. Toxichem Krimtech 2010;77:189 90. [33] McIntyre IM, Nelson CL, Schaber B, Hamm CE. Antemortem and postmortem methamphetamine blood concentrations: three case reports. J Anal Toxicol 2013;37:386 9. [34] Olsen KN, Luckenbill K, Thompson J, Middleton O, Geiselhart R, Mills KM, et al. Postmortem redistribution of fentanyl in blood. Am J Clin Pathol 2010;133:447 53.
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[35] Moriya F, Hashimoto Y. Postmortem diffusion of drugs from the bladder into femoral venous blood. Forensic Sci Int 2001;123:248 53. [36] Lemaire E, Schmidt C, Dubois N, Denooz R, Charlier C, Boxho P. Site-, technique-, and time-related aspects of the postmortem redistribution of diazepam, methadone, morphine, and their metabolites: interest of popliteal vein blood sampling. J Forensic Sci 2017;62:1559 74. [37] Fleby S, Olsen J. Comparative studies of postmortem barbiturate and meprobamate in vitreous humor, blood and liver. J Forensic Sci 1969;14:507 14. [38] Sturner WQ, Garriott JC. Comparative toxicology in vitreous humor and blood. Forensic Sci 1975;6:31 9. [39] Vogel J, Hodnett CN. Detection of drugs in vitreous humor with an enzyme immunoassay technique. J Anal Toxicol 1981;5:307 9. [40] Ziminski KR, Wemyss CT, Bidanset JH, Manning TJ, Lukash L. Comparative study of postmortem barbiturates, methadone, and morphine in vitreous humor, blood, and tissue. J Forensic Sci 1984;29:903 9. [41] Bazmi E, Behnoush B, Akhgari M, Bahmanabadi L. Quantitative analysis of benzodiazepines in vitreous humor by high-performance liquid chromatography. Sage Open Med 2016;4:1 7. [42] Metushi IG, Fitzgerald RL, McIntyre IM. Assessment and comparison of vitreous humor as an alternative matrix for forensic toxicology screening by GC-MS. J Anal Toxicol 2016;40:243 7. [43] De Letter EA, De Paepe P, Clauwaert KM, Belpaire FM, Lambert WE, Van Bocxlaer JF, et al. Is vitreous humor useful for the interpretation of 3,4methylenedioxymethamphetamine (MDMA) blood levels? Experimental approach with rabbits. Int J Legal Med 2000;114:29 35. [44] Be´valot F, Cartiser N, Bottinelli C, Fanton L, Guitton J. Vitreous humor analysis for the detection of xenobiotics in forensic toxicology: a review. Forensic Toxicol 2016;34:12 40. [45] Kennedy C. Validation of diphenhydramine, tramadol and methadone in vitreous humor analysis and comparison to blood and brain concentrations. Master’s thesis. Lincoln: University of Lincoln (UK); 2016. [46] Baselt RC. Disposition of toxic drugs and chemicals in man. 8th ed. Foster City: Biomedical Publications; 2008. [47] Rohrig TP, Hicks CA. Brain tissue: a viable postmortem toxicological specimen. J Anal Toxicol 2015;39:137 9. [48] Skov L, Johansen SS, Linnet K. Postmortem quetiapine reference concentrations in brain and blood. J Anal Toxicol 2015;39:557 61. [49] Skov L, Holm KMD, Linnet K. Nitrobenzodiazepines: postmortem brain and blood reference concentrations. Forensic Sci Int 2016;268:39 45. [50] Skov L, Holm KMD, Johansen SS, Linnet K. Postmortem brain and blood reference concentrations of alprazolam, bromazepam, chlordiazepoxide, diazepam, and their metabolites and a review of the literature. J Anal Toxicol 2016;40:529 36. [51] Nedahl M, Johansen SS, Linnet K. Reference brain/blood concentrations of citalopram, duloxetine, mirtazapine and sertraline. J Anal Toxicol 2018;42:149 56. [52] Tominaga M, Michiue T, Ishikawa T, Kawamoto O, Oritani S, Ikeda K, et al. Postmortem analyses of drugs in pericardial fluid and bone marrow aspirate. J Anal Toxicol 2013;37:423 9. [53] Rodda LN, Volk JA, Moffat E, Williams CM, Lynch KL, Wu AHB. Evaluation of intraosseous fluid as an alternative biological specimen in postmortem toxicology. J Anal Toxicol 2018;42:163 9.
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[54] Baud FJ, Buisine A, Bismuth C, Galliot M, Vicaut E, Bourdon R, et al. Arterio-venous plasma concentration differences in amitriptyline overdose. J Toxicol Clin Toxicol 1985;23:391 406. [55] Sato S, Baud FJ, Bismuth C, Galliot M, Vicant E, Buisine A. Arterial-venous plasma concentration differences of meprobamate in acute human poisonings. Hum Toxcol 1986;5:243 8. [56] Robertson MD, Drummer OH. Postmortem distribution and redistribution of nitrobenzodiazepines in man. J Forensic Sci 1998;43:9 13.
13
Until recently, the established approach to the interpretation of postmortem drug concentrations was thought to be a simple process. The concentration of a drug and/or metabolite, measured at autopsy, was static and could be simply compared to established therapeutic and/or toxic concentration ranges in living subjects. This simplistic approach has been proven to be wrong. The postmortem concentrations of drugs have been demonstrated to exhibit a site (anatomical) dependency [1]. Heart blood drug concentrations for many drugs are usually greater than the measured concentrations from peripheral sites; such as femoral veins. To further complicate the matter, the concentrations of drugs in postmortem specimens frequently increase with the increasing postmortem interval. The change in the peripheral specimens appears to be of less magnitude and at a slower rate than that of heart blood drug concentrations. There are energy-dependent processes that maintain drug concentration gradients during life, after death these processes cease and changes in the gradient are expected to occur. Drugs will undergo diffusion down concentration gradients. Drugs in high concentrations in various tissue reservoirs; such as liver, lung, and heart will be separated from these protein bound sites and passively diffuse into adjacent tissue and central blood vasculature [2]. Another reservoir with orally ingested drugs is the stomach [3] with diffusion into the lower lobe of the left lung and left lower lobe of the liver and into the heart tissues. This process has been termed postmortem diffusion or postmortem redistribution (PMR). The term PMR was used by Koren and MacLeod in the title of their 1985 [4] paper on changes in digoxin concentration after death in a rat. However, long before the prodigious work of Prouty and Anderson [1], there were observations and reports in the literature, decades before, of these anatomical site differences in blood drug concentrations. Curry and Sunshine [5] reported
Postmortem Toxicology. DOI: https://doi.org/10.1016/B978-0-12-815163-1.00013-7 © 2019 Elsevier Inc. All rights reserved.
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large differences in barbiturate concentrations in central blood samples as compared to a peripheral sample. They were one of the first to suggest the utilization of peripheral blood sample and suggest that further research in this area of postmortem toxicology was needed. Gee et al. [6] corroborated Curry and Sunshine’s data. They too gave a cautionary note that the area/ site of collection is an important consideration for interpretation. Holt and Benstead [7] made the observation that three different postmortem samples collected from three different anatomical sites in the same body contained different concentrations of digoxin and speculated that the drug may have been redistributed in the body after death. Vorphal and Coe [8] compared ante- and postmortem digoxin concentrations in 27 subjects. They observed that the postmortem digoxin concentrations were higher than the antemortem concentrations. They also noted differences in the postmortem samples collected; heart, femoral, and subclavian blood samples and that the heart blood samples had the highest concentration of digoxin. They concluded that this was a “special case” in that digoxin is highly bound to the myocardium and that the drug probably diffused from the cardiac tissue into the heart blood. The body of knowledge evolving around PMR of drugs began to demonstrate that the redistribution depended on many factors; the two predominate ones were the anatomical site of the blood collection and the postmortem interval. Brandt [9] presented data at the American Academy of Forensic Sciences involving tricyclic antidepressants (TCAs). The study concluded that the concentration of TCAs was a function of the anatomical site of collection and the length of the postmortem interval. One of the sentinel cases which brought the phenomena of PMR to the forefront of the scientific community occurred in 1987 (Rohrig—Personal Communication and [10]). A 63-yearold female hospitalized in a state facility died overnight. At autopsy, the only anatomically significant finding was a large brain tumor, of a size and location that would explain the woman’s death. Routine toxicology was performed and desipramine, which was prescribed, was detected. However, the heart blood concentration was 6.3 mg/L, and in a range that could be considered lethal. Since the care providers were in control of the decedent’s medication, an extensive investigation was undertaken; including a careful review of pharmacy records, which did not reveal overdispensing. A standard pharmacokinetic equation [Dose 5 weight (kg) 3 volume of distribution (L/kg) 3 blood concentration (mg/L)] suggested a large amount
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of drug was ingested (estimated dose: 6600 mg or 264 25 mg tablets); which exceed the available stock of desipramine. The case suggested that the postmortem blood concentration may not necessarily reflect the antemortem concentration of the drug. This finding prompted an extensive study covering a wide variety of drugs (n 5 45) and the impact of the anatomical site of collection and the postmortem interval [1]. Their study involved collection of a heart blood sample, via a cardiac stick, that was sent with the body to the morgue. At autopsy additional specimens were collected; heart blood, femoral blood, as well as other biological fluids and tissues. The authors concluded that the drug concentration of weakly basic drugs had a tendency to increase with the postmortem interval and that the central blood concentrations tend to be greater than the peripheral blood drug concentrations. They also noted that the drug concentration in the peripheral samples also increased over the postmortem interval. They further cautioned that calculation of dose from a heart blood sample should be avoided. In addition to drugs passively moving down a concentration gradient; from high concentration in tissue into surrounding blood supply other factors will influence drug redistribution. These authors and others [2,11 14] have concluded that the chemical characteristics of the drug also play a major role in the propensity to undergo PMR. Drugs with a high volume of distribution (Vd . 3 L/kg), weakly basic in chemical nature (pKa . 7) and have a high octanol:water coefficient; that is, are highly lipophilic and make the drug more likely to redistribute. The longer the postmortem interval, the more likely there will be an increase in concentration for drugs that exhibit PMR. Muscle rigor and putrefactive gas build-up, due to decomposition, can compress peripheral vasculature and may cause postmortem circulation of blood and potentially alter the drug distribution. Jones and Pounder [15] illustrate in a case study of one decedent that not all drugs will exhibit same anatomical site differences in concentration. The blood concentrations of imipramine and its metabolite desipramine in central blood vessels were 50% 760% higher as compared to concentrations the in peripheral vasculature. The site to site variation of diphenhydramine and codeine were much less dramatic, ranging from 2.5 to 6 times higher in the pulmonary vein as compared to the subclavian vasculature. However, the blood concentrations for acetaminophen and ethyl alcohol exhibited little variation from site to site. The author presented additional case study data that
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demonstrate substantial site differences in blood drug concentrations for some but not all drugs [16]. Prouty and Anderson [17] confirmed the insignificant variation in heart blood to femoral blood ethyl alcohol concentrations. In the cases that did vary more than 0.02 g%, the specimens had unique characteristics; significant differences in physical appearance, trauma to the area of collection, gross differences in hematocrit, or large volume differences in the two specimens collected. A heart blood to femoral blood (HB:FB) or central blood to peripheral blood (C:P) ratios are considered good indicators of a drug with the probability to undergo PMR; the higher the ratio the more likely the drug will undergo redistribution [18,19]. A drug with a high C:P ratio is thought to have the propensity to undergo substantial redistribution after death. However, a low C:P ratio (less than unity) does not necessarily indicate the drug will not undergo redistribution. Dalpe-Scott et al. [20] published the C:P ratio for 113 drugs from 320 postmortem cases. The central blood concentration was higher in most cases the C:P ratio ranged from greater than 1 up to 21 times higher diphenhydramine was the highest at 21-fold. However, six drugs had ratios # 1; ephedrine, hydrocodone, hydroxyzine, metoprolol, procyclidine, and trifluroperazine that would be expected to undergo some redistribution. There have been other reports of drugs with C:P ratios of .1, which would not be expected to undergo redistribution; for example, salicylic acid [18], carisoprodol [21], and tramadol [22]. McIntyre and Escott [23] have proposed a liver to peripheral blood (L:P) ratio as a new marker for PMR. They suggest that a ratio exceeding 20 is indicative of the drug undergoing redistribution, where a ratio of less than 5 indicating no propensity to undergo redistribution. In more recent papers, McIntyre [24 26] proposes the concept of a PMR factor (F), in which he characterizes as having a direct relationship to the corresponding antemortem concentration of the drug. The mathematical relationship suggested is AM (antemortem concentration) 5 P (peripheral postmortem concentration)/F (PMR factor or L:P ratio). However at this point, there is minimal data to support the validity of this concept; McIntyre does suggest further work needs to be undertaken to support this hypothesis. In addition to the chemical nature of the drug, the anatomical site blood is drawn from has an influence due to the anatomy. The vast majority of studies have come to the conclusion that the various factors influencing the PMR of drugs include: the condition of the body; the physical barriers—decomposition
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and/or trauma, allowing for microbial invasion, residual enzymatic activity, the pH of tissues, and the postmortem movement of blood due to putrefaction, rigor mortis, and gravitydependent blood flow. Peripheral blood samples are generally collected from the femoral vein. These veins are a preferred anatomical site due to the larger number of values in the femoral vein as compared to the vasculature as it becomes more central. The valves in the veins tend to restrict the postmortem movement of blood and passive diffusion of the drug through the vasculature. There have been more recent observations that “milking” of the veins to get a larger blood sample will overcome the physical barrier provided by the values and the drug concentrations in these “milked” samples tend to be more reflective of a central specimen. Some practitioners have suggested that “Clamping” the femoral vein prior to collection will prevent contamination from more central sources such as iliac vessels or the inferior vena cava. Hargrove and McCutcheon [27] undertook a study to determine whether or not a “blind stick” femoral blood samples were significantly different from blood collected from cut-down clamped femoral vessels. They evaluated eight different drugs representing four different drug classes. There were three serotonin-reuptake inhibitors: sertraline, paroxetine, and citalopram; two different benzodiazepines: diazepam and alprazolam; two antihistamines: diphenhydramine and promethazine, and one opiate: hydrocodone. The authors found that the clamped femoral blood concentrations and the blind stick concentrations were found to be in good agreement. All four drug classes had a ratio of approximately 1.0. They concluded that the “style” of collection of the peripheral blood sample did not have a significant impact on the resulting femoral blood drug concentrations. Lemaire et al. [28] investigated the impact on drug concentrations of blind stick and dissection/clamping blood collection techniques for sampling of subclavian and femoral sites. They evaluated the impact of the collection techniques on three drugs; diazepam, methadone, and morphine. The blood concentrations of diazepam and methadone were lower with the blind stick as compared to the dissected/clamped vessel for both the subclavian and femoral veins. This is in conflict with what Hargrove and McCutcheon found for diazepam in femoral sample; that there was no significant difference in concentration between the two techniques utilized for blood collection. Morphine concentrations in Lemaire et al. [29] study were lower from the subclavian site with the dissection and clamping technique, as compared to a blind stick; whereas with the blind
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stick technique, the morphine concentrations were lower at the femoral site as compared to collection by dissection/clamping of the vessel. Hargrove and Molina [30] did not observe any significant variation in morphine concentration from blood collected from the femoral vessel, regardless of collection techniques; blind stick or dissection/clamping. Although the variation will effect the calculation of a C:P ratio, the differences should not grossly impact in a negative manner the interpretation of the drug result. A fair amount of postmortem toxicological analyses are performed offsite at a reference laboratory. McLemore et al. [31] investigated the effects of transport conditions on the collected blood samples. They examined three different blood specimen/ shipping procedures to evaluate the impact on drug concentrations. The authors collected femoral blood via a “blind stick” in the inguinal area of the body and shipped to the laboratory at ambient temperature. A second “blind stick” in the same area was performed and the collected femoral blood was shipped to the laboratory on dry ice. An iliac blood sample was obtained on the opposite side by direct visualization and clamping the vessel prior to blood collection. This sample was shipped to the laboratory on dry ice. The total number of autopsy cases evaluated was 112, with 78 different drug or drug metabolites detected. The authors did not find any statistical difference between the three collection/shipping methods. However, in 49 of the cases, the “blind stick” femoral sample shipped at ambient temperature was positive, while the iliac, “blind stick” femoral shipped on dry ice or both were negative. The drug or drug metabolite in which this occurred in multiple cases was delta9-tetrahydrocannabinol, sertraline/norsertraline and fluoxetine/ norfluoxetine, and hydromorphone; and multiple other analytes in one or two cases. The authors suggest that analyte instability due to the freeze/thaw cycle may be the reason for the negative results. Peripheral blood samples are preferred for quantitative analyses in that they will more closely reflect the antemortem concentration. A more recent study by Gerostamoulos et al. [32] evaluated a large number of drugs (n 5 52) and the impact of the postmortem interval. Their study compared “admission” blood (antemortem) to femoral autopsy blood drug concentrations. The postmortem interval ranged up to 164 hours (6.4 days), with a mean value of 64 hours. They found that more than 45% of the drugs had a change in concentration that was greater than or equal to 10%. The selective serotonin-reuptake inhibitors (venlafaxine, mirtazapine, and paroxetine) had
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average increases of approximately 30% irrespective of the postmortem interval. Their overall conclusion was that there may be a rise in femoral blood drug concentration irrespective of the postmortem interval. McIntyre et al. [33] made similar observations with methamphetamine and amphetamine, albeit with a small sample size (n 5 3 and 2, respectively). The antemortem samples were drawn between 7 and 22 minutes prior to pronouncement of death and the postmortem interval ranged from 5.25 to 30.5 hours. The peripheral to antemortem blood ratios averaged 1.51 and 1.50 for methamphetamine and amphetamine, respectively. In a study looking at the PMR of fentanyl, Olsen et al. [34] evaluated seven cases in which femoral blood was collected at two intervals; shortly after death and at autopsy. The mean collection times were 4.0 and 21.6 hours following death, respectively. All samples demonstrated a rise in fentanyl concentration between the two collection time, however, the rate of rise varied dramatically between the cases; minimal change in concentration, 5.0 5.1 µg/L to a dramatic change in concentration of 4.7 52.5 µg/L. PMR is site dependent with drug diffusing from tissue depots with high drug concentrations into the blood compartment; the central (Heart) blood compartment being the most effected. However, Moriya and Hashimoto [35] described a case where the femoral drug blood concentrations were presumably increased due to diffusion of the drug from the bladder. They reported a case of a 16-year-old male who was found dead in a stream. The decedent had a history of OTC (over-the-counter) drug abuse. Autopsy did not reveal an anatomical cause of death; one significant finding was that the bladder contained 600 mL of urine. The cause of death was certified as “Drowning after OTC drug abuse.” The concentration of diphenhydramine and dihydrocodeine was higher in the femoral blood as compared to the heart blood drug concentrations. They hypothesized that during the comatose period, a large volume of urine collected containing high concentrations of the drugs. The drugs then diffused from the bladder into the femoral blood compartment. Femoral blood specimens are routinely used for quantitative analyses to minimize the impact of PMR. However as noted by Prouty and Anderson [1] and others, they have demonstrated that there may still be an increase in femoral blood drug concentration over the postmortem interval. To address the challenge of PMR, many researchers have evaluated alternate specimens to assist in the interpretation of a case. These alternate specimens are remote to the “central” part of the body,
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and therefore would be resistant to passive diffusion of a drug from the high concentration depots. These alternative specimens include popliteal blood samples, which are distal to a femoral blood sample, vitreous fluid, brain tissue, and new areas of investigation include cerebral spinal fluid, intraosseous fluid (IOF), and synovial fluid. Lemaire et al. [29] has proposed that popliteal vein blood is less prone to PMR as compared to FB. This is thought to be because the popliteal vein is more distal site to the central body, as compared to the femoral vein. To sample the blood, given the deep anatomical location in the leg, the dissection was necessary to access the vein; the vessel was then clamped prior to collection, to prevent admixture of blood in the femoral vein. The authors evaluated 30 autopsy cases containing one or more of the following drugs; diazepam, methadone, and morphine. They concluded that blood sampled from this anatomical site was less prone to PMR as compared to FB. There appears to be no significant difference between left and right popliteal blood samples [28]. In a later study [36], they evaluated the impact of PMR on the same drugs, in 57 autopsy cases, over time. The authors conclude that blood from the popliteal vein was less prone to PMR as compared to blood from other anatomical sites, including FB. Vitreous humor has been looked as an alternative matrix for postmortem toxicology over the last five decades [37]. Sturner and Garriott [38] examined blood and vitreous in 56 cases of decedents dying from drug overdose and other causes. The challenges early on were the small sample size available and the sensitivity of the analytical procedures. However, with the advent of immunoassay techniques [39,40], (high-performance liquid chromatography [41] and gas chromatography mass spectrometry [42]), these challenges no longer existed and more research was conducted on comparing vitreous drug concentrations to paired blood concentrations. De Letter et al. [43] in a rabbit dosing study gave IV 3,4-methylenedioxymethamphetamine (MDMA) to rabbits and compared the antemortem blood concentration to the vitreous humor concentration in animals held at room temperature. The postmortem MDMA concentrations in the vitreous were closer to the antemortem blood concentrations than the postmortem cardiac blood. The authors suggest that this preliminary animal study indicated that vitreous humor may be a viable sample to address the challenges of PMR and predict the antemortem drug concentration. Be´valot et al. [44] conducted a review of using vitreous humor as a matrix for the detection of drugs in
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postmortem cases. The authors suggest that vitreous humor has several advantages in forensic toxicology; it is less prone to PMR, it is easy to collect, has few interfering substances in the analytical analyses, and is stable over the postmortem interval. The authors provide an extensive table presenting blood concentrations (cardiac and peripheral) and vitreous humor concentrations for a variety of drugs. They suggest further investigation is needed to fully assess the viability of this sample as a tool to better predict the antemortem blood concentration in the decedent. Kennedy [45] added to this body of knowledge in her Master’s thesis. The author investigated the distribution of diphenhydramine, tramadol, and methadone in vitreous humor, blood (heart blood and femoral), and brain tissue. The conclusion from the study was that the average correlation ratios showed diphenhydramine and methadone were found in higher concentrations in blood (heart and femoral) and brain as compared to vitreous humor. Whereas, the average correlation ratio for tramadol was found higher in the vitreous than in blood, with nearly equal concentrations in vitreous humor and brain. Additional data are needed to fully assess the viability of this specimen in it utility to address the challenges of PMR. Brain tissue may be a valuable specimen in assisting in the interpretation of postmortem toxicological results. The protected and isolated position of the brain may eliminate the challenges of PMR and delay or attenuate residual enzymatic activity on some compounds which may artificially lower their concentration. The tissue is more immune to decomposition allowing for the detection and quantitation in the tissue as compared to cavity fluid or organ tissue within the thoracic/ abdominal cavity. However, there are a limited amount of data comparing brain drug concentrations to blood concentration, specifically femoral blood concentrations. Baselt [46] has some brain data in individual monographs; however, there is a paucity of data as to the quantitative distribution of drugs in the brain. Rohrig and Hicks [47] presented data from heart, femoral blood, and brain tissue for 30 drugs and drug metabolites in cases submitted for autopsy examination. The authors found a positive correlation between blood concentrations to brain concentrations. However, this study did not breakout brain concentrations found in cases where the drug was the direct cause of death or contributory versus noncontributory to the death. There are a limited number of studies that provide a breakdown of brain concentrations where the role of the drug in the death was delineated along with the brain concentration. These
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studies provide postmortem reference ranges in blood and brain tissue, thus minimizing the impact of PMR; quetiapine [48], nitrobenzodiazepines [49], alprazolam, bromazepam, chlordiazepoxide, diazepam, and their metabolites [50] and citalopram, duloxetine, mirtazapine, and sertraline [51]. There are some emerging data for drug analyses in bone marrow aspirates or IOF and their utility to be somewhat resistant to PMR. Tominaga et al. [52] evaluated bone marrow aspirate as a substitute of blood as a proposed specimen when blood was not available. They opined that aspirate bone marrow samples contained a large amount of peripheral blood, and therefore would be a suitable alternative substitute and may be useful in addressing PMR. IOF (bone marrow aspirate) has recently been investigated as an alternative specimen for toxicological analyses that is immune from PMR, due to its isolation from surround tissue. IOF was collected from right and left tibias and humerus of 29 decedents, along with routine autopsy samples [53]. Both specimens were screened with immunoassay for amphetamines, benzodiazepines, cannabinoids, cocaine, fentanyl analogs, methadone, methamphetamine, opioids, oxycodone, phencyclidine, and TCAs. There was a strong correlation between the screen result in both cardiac blood and IOF; ranging from a low of 63% to 100%, with the majority having a 100% correlation. Methamphetamine, amphetamine, and tetrahydrocannabinol positive screen results were confirmed in blood, using gas chromatography mass spectrometry; there too existed a strong positive correlation of 100%. The author also did not observe any site differences in the qualitative screen result; that is, right, left tibia, and humerus IOF. They go on to suggest that not only being a possible matrix for mitigating the impact of PMR, they further opine that IOF may be potentially less-compromised tissue in decomposed and/or traumatized bodies and that further study is needed. In addition to a drug undergoing PMR, there may be other confounding factors that influence site dependency of drug concentrations. Acute drug exposure from an accidental or suicidal overdose causing death may result in an incomplete distribution of the drug throughout the body. Baud et al. [54] evaluated 24 patients who present in a comatose state due to an acute amitriptyline overdose. The author measured amitriptyline concentrations in paired femoral arterial and venous blood samples, finding significant different concentrations. Sato et al. [55] found similar results in paired femoral arterial and venous blood samples in 35 patients who were admitted to the hospital for an acute meprobamate overdose.
Chapter 13 POSTMORTEM REDISTRIBUTION
Residual enzymatic activity may alter drug concentrations. The enzymes may be endogenous; residual tissue enzymatic activity, gut microflora possessing enzymatic activity and released during the putrefactive process or traumatic injury or bacterial enzymatic activity may also be introduced by penetrating trauma. Robertson and Drummer [56] found various nitrobenzodiazepines were metabolized “postmortem” by a variety of bacteria which possessed nitroreductase enzymes; metabolizing the nitrobenzodiazepine to their respective 7-amino metabolite.
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