Skip to main content
NCBI home page
Journal of Analytical Toxicology logoLink to Journal of Analytical Toxicology
. 2026 Sep 22;50(9):bkag083. doi: 10.1093/jat/bkag083

Thinking beyond blood: brain concentrations and brain–blood ratios in postmortem toxicology

Kathrine Østerballe Skov 1, Mikayla Zoë van der Meer 2, Michael Nedahl 3, Marie Katrine Klose Nielsen 4,✉
PMCID: PMC13686759  PMID: 42773705

Abstract

Toxicological analysis is an integral part of forensic death investigations. However, analysis is sometimes complicated by postmortem changes, and blood might not always be useable or available due to postmortem redistribution or degradation. In these cases, brain tissue can be useful as the brain is more protected against trauma, putrefaction, postmortem redistribution, skeletonization, and severe blood loss. However, reference concentrations of drugs in brain tissue are still scarce. This study aimed to report brain concentrations and brain–blood ratios for 122 compounds including drugs of abuse, pharmaceuticals, and metabolites frequently detected in forensic autopsy cases. In total, 2264 cases were collected over an 11-year period and retrospectively categorized as having either toxic or therapeutic levels of detected compounds based on blood concentrations. Toxic and therapeutic concentrations showed considerable overlap in both blood and brain due to drug tolerance and multi-drug combinations. Brain–blood ratios were highest for compounds with direct function on the central nervous system, especially antidepressants and sedative-hypnotics. The reported brain concentrations and brain–blood ratios can serve as reference values for interpretation of drug concentrations in brain tissue and the evaluation of cause of death in future forensic investigations.

Introduction

The field of forensic toxicology is under continuous development through advances in analytical methods and improvements in interpretation of results to ensure quality and reliability of forensic results in the medico-legal investigation [1]. Postmortem toxicology is used in forensic investigations to assess potential drug use prior to death, therapeutic medicinal use, or the potential contribution of drugs to the cause of death [2]. However, postmortem drug concentrations are affected by several antemortem and postmortem effects, such as individual metabolism and excretion, postmortem redistribution, and decomposition [3–5]. These postmortem changes can complicate forensic investigations, and, in some cases, toxicological analysis must rely on other postmortem biological specimens because peripheral blood might not be available due to putrefaction, burns, or large blood losses [1, 2, 6–8].

Brain tissue is a useful alternative matrix for toxicological analysis in postmortem cases where peripheral blood is no longer available or viable for analysis [9–11]. Due to its more secluded position, the brain is more often protected against postmortem changes such as postmortem redistribution and decomposition. Additionally, many drugs of abuse and pharmaceuticals exert their effects through the central nervous system (CNS) leaving the brain as their site of action [12]. Following drug consumption and absorption, drug distribution from blood into specific tissue such as brain is determined by the affinity between drug and tissue components and drug transporters [13]. The blood–brain barrier (BBB) functions as one of the major protective barrier layers of the CNS and has an important regulative influence on drug delivery from the blood to the brain parenchyma [13, 14]. The BBB consists of endothelial cells forming capillary walls that extend throughout the brain parenchyma as a protective barrier against harmful substances such as neurotoxins and plasma proteins that can be damaging to neural tissue [14]. In addition, its barrier function consists of drug transporters such as the P-glycoprotein (P-gp) transporter and metabolic barriers expressing several drug-metabolizing enzymes acting as determining factors in drug access across the BBB [14, 15]. As such, brain penetration of a drug is dependent on several factors such as physiochemical properties and interaction with the P-gp transporter or drug-metabolizing enzymes such as cytochromes P450 at the BBB [16, 17]. Compounds intended to act within the CNS are typically designed to ensure high permeability across the BBB [15], which is facilitated through either lipid-mediated free diffusion or carrier- or receptor-mediated transport [18, 19]. Consequently, brain tissue is a relevant alternative matrix for toxicological analysis. However, interpretation of drug concentrations in brain tissue requires reference data where concentrations in brain and peripheral blood are compared [6]. Careful interpretation of toxicological results is fundamental in forensic investigations and reference concentrations observed under toxic and therapeutic conditions are important for interpretation of postmortem drug concentrations [4]. Comprehensive lists of reference drug concentrations in postmortem blood and median drug concentrations in postmortem matrices have previously been published [1, 20–25]. Additionally, reference brain concentrations and brain–blood ratios focusing on selected drugs of abuse, antipsychotics, and antidepressants have previously been published [26–36], but reference brain concentrations for many drugs of abuse and pharmaceuticals are still limited compared to reference concentration in blood. Moreover, most published case studies and compilations focus on high drug concentrations such as in lethal cases, but postmortem reference concentrations are also needed for therapeutic concentrations [1]. Thus, the aim of this article was to evaluate toxic and therapeutic brain concentrations and brain–blood ratios from frequently detected drugs, pharmaceuticals, and metabolites in forensic postmortem autopsy cases from Eastern Denmark.

Materials and methods

The Department of Forensic Medicine, University of Copenhagen, carries out autopsies of decedents as part of forensic death investigations by local police authorities. The present study comprises retrospective data from 2264 autopsy cases subjected to toxicological investigations between January 2014 and March 2025. The dataset includes paired blood and brain concentrations of 122 compounds frequently detected in autopsy cases during toxicological analysis performed at the Section of Forensic Chemistry.

Case selection and classification

Cases were included if quantified results were available for paired blood and brain samples, and if there were three or more cases per compound. Data for some published drugs of abuse, pharmaceuticals, and metabolites were also included if the number of cases exceeded the number of cases originally published [26–34]. The antipsychotics chlorprothixene, clozapine, olanzapine, and quetiapine were not included, as reference concentrations for these drugs were recently published [37].

All cases were retrospectively classified into two categories depending on whether the observed postmortem drug blood concentration was within toxic or therapeutic levels based on toxicological details and the final forensic medical statement, as ruled by the forensic pathologist. Cases were categorized as toxic if it was estimated that the blood concentration of the drug of abuse or pharmaceutical was within toxic ranges and/or had contributed to death either alone or in combination with other drugs of abuse, pharmaceuticals, or disease. Cases were categorized as therapeutic if the postmortem analyte blood concentration was within therapeutic ranges [20] and not considered to have any contribution to cause of death. Metabolites were categorized according to their parent drug, and the sum of the parent drug and active metabolite was used in the toxicological report to assess if a toxic concentration was reached. If a compound appeared in less than three cases in either the therapeutic or toxic category, the results for therapeutic and toxic were combined in one group.

Collection of postmortem samples

Decedents were stored at 5°C and autopsy was typically performed within 4 days. During autopsy, biological specimens, including peripheral blood and brain tissue, were collected for toxicological investigation and stored at –20°C prior to analysis. Two femoral blood samples of 4–8 mL were collected without ligation of the iliac vein and stored in vacutainers with sodium fluoride and potassium oxalate. Brain tissue samples of 5–20 g were collected from the frontal cerebral cortex and stored with no preservatives.

Sample preparation and toxicological analysis

Gray matter was manually separated from the brain tissue samples with a scalpel, and 500 mg was diluted (1:3) with LC–MS-grade water and homogenized using a gentleMACS dissociator (Milteney Biotic, Bergish Gladbach, Germany). The brain homogenate was centrifuged at 2000 g and 20°C for 10 minutes and transferred to new tubes. Whole blood and brain homogenate samples were prepared in duplicates using a fully automated sample preparation method on a Tecan Freedom EVO 200 robotic platform (Tecan, Männedorf, Switzerland) or a Hamilton Microlab Vantage 2.0 liquid handling system (Hamilton, Bonaduz, Switzerland) [38]. Following sample preparation, blood and brain homogenate samples were analyzed using a previously described comprehensive systematic toxicological analysis strategy comprising five multi-target methods with quantification by ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) [39].

Data processing

Results from quantitative analysis of drugs in postmortem blood and brain were extracted from the laboratory information management system (LIMS). Drugs of abuse, pharmaceuticals, and metabolites that had been quantified in at least three cases in both blood and brain were included and the data was presented as 10th–90th percentiles intervals and median values for the blood concentration, brain concentration, and brain–blood ratio.

Results and discussion

A total of 2264 autopsy cases were included in the current study, providing paired concentrations and brain–blood ratios for 122 commonly encountered compounds in forensic cases. Those compounds consisted of 9 analgesic/anesthetics, 18 antidepressants, 11 antihistamines, 11 antipsychotics, 8 cardiovascular drugs, 16 opioids, 21 sedative-hypnotics, which included benzodiazepines, 9 stimulants, and 19 drugs that did not fit in one of the above categories. Methadone, paracetamol, and N-demethyldiazepam were the most frequently detected compounds. Intoxication was considered as the cause of death or to have contributed to death in 45% of cases with the majority of autopsy cases involving multiple drugs in both the toxic and therapeutic categories.

Of the 122 detected compounds, 59 compounds had sufficient data to allow classification into therapeutic and toxic categories, findings of 33 compounds were considered therapeutic, the findings of flubromazelam were classified as toxic, while classification was not possible for the remaining 29 compounds due to limited case numbers in one or both categories. Table 1 provides an overview of findings of all compounds distributed into nine drug groups, including their respective median values and 10th–90th percentiles in blood concentrations, brain concentrations, and brain–blood ratio. As shown in Table 1, a substantial overlap between the therapeutic and toxic categories was observed for both concentrations and brain–blood ratios. The median brain–blood ratio ranged from 0.07 to 26 across all compounds, where the lowest median brain–blood ratios (<0.01) were observed for ropivacaine and fexofenadine, and the highest median brain–blood ratios (>10) were observed for dextromethorphan, vortioxetine, scopolamine, norfluoxetine, and fluoxetine.

Table 1.

Median and 10th–90th percentiles for blood and brain concentrations and brain–blood ratios for 122 compounds distributed into nine drug groups. For each case, the drug findings were categorized as toxic or therapeutic. Findings were combined in one group if there were less than three cases in either the toxic or therapeutic category.

Group Drug N Category Blood concentration (mg/kg)
 Brain concentration (mg/kg)
 Brain–blood ratio
Median 10th–90th percentile Median 10th–90th percentile Median 10th–90th percentile
Analgesic/anesthetic Bupivacaine 11 Combined 0.84 0.38–3.2 0.68 0.25–1.7 0.68 0.42–0.90
Gabapentin 8 Toxic 44 25–70 18 3.4–36 0.48 0.087–0.68
50 Therapeutic 11 1.8–28 3.7 0.69–11 0.46 0.13–0.69
Ibuprofen 11 Combined 13 9.0–90 6.0 5.0–17 0.47 0.35–0.90
Ketamine 7 Toxic 1.1 0.21–1.8 0.82 0.3–4.1 1.3 0.83–2.3
37 Therapeutic 0.33 0.084–0.86 0.40 0.075–3.1 1.5 0.58–6.7
Lidocaine 199 Therapeutic 0.19 0.030–1.2 0.16 0.030–1.2 0.91 0.33–2.5
Paracetamol 17 Toxic 290 130–1150 160 49–670 0.62 0.41–0.69
414 Therapeutic 15 7.0–42 9.0 5.0–23 0.67 0.37–0.86
Pregabalin 7 Toxic 17 5.5–45 5.2 2.1–9.6 0.29 0.17–0.60
51 Therapeutic 5.0 1.5–11 1.7 0.60–3.6 0.35 0.17–0.53
Ropivacaine ≤5 Therapeutic 3.5 1.1–29 0.26 0.20–0.34 0.070 0.022–0.36
Salicylic acid 27 Combined 43 15–170 11 5.0–68 0.29 0.19–0.39
Antidepressant Amitriptylinea 13 Toxic 1.2 0.30–5.3 7.1 1.0–37 4.1 2.6–12
38 Therapeutic 0.14 0.031–0.49 0.44 0.11–1.5 3.4 2.4–5.8
Citaloprama 48 Toxic 0.99 0.46–2.4 3.3 1.2–6.1 3.3 2.0–4.8
114 Therapeutic 0.22 0.024–0.57 0.76 0.11–2.3 3.9 2.7–5.7
N-Demethylcitalopram 44 Toxic 0.19 0.083–0.43 0.32 0.089–0.57 1.6 0.94–2.2
58 Therapeutic 0.080 0.019–0.20 0.16 0.047–0.38 2.0 1.3–3.4
Clomipramine ≤5 Therapeutic 0.25 0.23–0.42 1.0 0.62–2.7 4.0 2.6–6.1
N-Demethylclomipramine ≤5 Therapeutic 0.38 0.13–0.49 2.8 0.97–3.4 7.4 7.0–8.1
Duloxetinea 15 Toxic 0.25 0.087–0.35 1.8 0.69–3.4 7.9 5.2–12
42 Therapeutic 0.081 0.024–0.24 0.69 0.20–2.1 8.3 5.7–14
Fluoxetine ≤5 Toxic 2.1 0.55–6.2 19 4.6–22 5.6 4.0–11
10 Therapeutic 0.31 0.043–0.81 3.3 0.46–9.3 12 8.7–20
Norfluoxetine ≤5 Toxic 0.85 0.72–2.4 7.8 5.7–14 7.0 4.6–12
10 Therapeutic 0.39 0.028–0.79 5.2 0.49–8.1 14 10–18
Imipramine 9 Combined 0.18 0.073–0.81 0.49 0.33–3.6 4.0 2.6–6.8
N-Demethylimipramine 9 Combined 0.078 0.029–0.76 0.48 0.23–4.7 6.3 5.7–14
Mianserin 28 Combined 0.083 0.023–0.14 0.23 0.067–0.51 2.4 1.7–6.8
Mirtazapinea 15 Toxic 0.76 0.17–2.4 1.2 0.24–6.6 1.8 1.2–4.6
137 Therapeutic 0.12 0.031–0.34 0.19 0.047–0.59 1.6 1.0–2.9
Nortriptyline 14 Toxic 0.53 0.34–1.87 4.3 2.4–15 6.8 3.7–13
55 Therapeutic 0.12 0.027–0.76 0.96 0.22–6.2 8.9 5.8–14
Paroxetine 10 Combined 0.23 0.003–2.3 3.4 0.041–25 12 7.7-18
Sertralinea 36 Toxic 0.55 0.30–2.5 4.7 2.8–15 7.9 5.2–13
125 Therapeutic 0.16 0.040–0.60 1.7 0.37–4.8 9.5 6.0–16
Venlafaxine 27 Toxic 2.0 0.82–22 3.2 1.1–28 1.7 0.82–2.4
52 Therapeutic 0.34 0.060–0.99 0.56 0.091–2.0 2.0 0.99–3.0
O-Desmethylvenlafaxine 26 Toxic 0.88 0.21–5.7 1.1 0.22–4.0 1.3 0.77–1.7
55 Therapeutic 0.36 0.088–1.2 0.54 0.16–1.6 1.7 1.2–2.3
Vortioxetine ≤5 Combined 0.11 0.059–0.27 1.2 0.90–2.7 14 8.6–19
Antihistamine Cetirizine ≤5 Toxic 0.55 0.21–0.69 0.15 0.065–0.25 0.35 0.29–0.37
51 Therapeutic 0.15 0.072–0.54 0.049 0.028–0.18 0.38 0.28–0.61
Chlorpheniramine ≤5 Therapeutic 0.013 0.003–0.023 0.063 0.014–0.11 5.0 3.7–5.7
Cyclizine ≤5 Combined 0.24 0.055–14 0.26 0.093–50 2.3 1.1–4.5
Desloratadine 7 Therapeutic 0.031 0.013–0.15 0.024 0.014–0.098 0.77 0.59–1.3
Diphenhydramine 20 Therapeutic 0.017 0.002–0.26 0.045 0.007–0.48 3.2 1.9–5.1
Doxylamine ≤5 Therapeutic 0.039 0.020–0.049 0.095 0.041–0.099 2.0 1.8–2.4
Fexofenadine ≤5 Therapeutic 1.1 0.55–1.4 0.050 0.034–0.22 0.080 0.056–0.16
Hydroxyzine ≤5 Toxic 0.27 0.21–0.54 1.0 0.62–3.5 3.9 2.9–6.1
27 Therapeutic 0.035 0.003–0.24 0.18 0.014–0.92 4.9 3.3–9.0
Loratadine ≤5 Therapeutic 0.003 0.002–0.005 0.004 0.003–0.010 2.1 1.6–2.2
Meclizine ≤5 Therapeutic 0.008 0.008–0.02 0.06 0.027–0.21 3.8 2.4–26
Promethazine 9 Toxic 0.23 0.058–0.94 0.95 0.26–4.5 4.1 2.7–7.4
69 Therapeutic 0.079 0.019–0.34 0.36 0.082–1.5 4.7 2.6–7.1
Antipsychotic Amisulpride ≤5 Combined 0.51 0.40–3.2 0.059 0.034–0.43 0.11 0.072–0.14
Aripiprazole ≤5 Toxic 0.16 0.13–0.17 0.79 0.58–0.91 4.6 3.6–6.9
38 Therapeutic 0.11 0.020–0.33 0.38 0.11–1.0 4.2 2.9–7.0
Flupentixol 11 Combined 0.013 0.002–0.027 0.12 0.013–0.16 7.5 5.1–9.1
Haloperidol 7 Toxic 0.040 0.020–0.055 0.083 0.054–0.11 2.9 1.1–5.0
35 Therapeutic 0.009 0.003–0.029 0.049 0.023–0.11 5.9 2.9–11
Levomepromazine 7 Combined 0.035 0.010–0.13 0.091 0.054–0.80 4.7 3.1–7.2
Perphenazine 7 Combined 0.013 0.005–0.18 0.11 0.044–1.1 7.3 5.6–10
Risperidone 20 Combined 0.005 0.003–0.018 0.013 0.007–0.030 2.4 0.96–4.1
9-Hydroxyrisperidone 62 Combined 0.008 0.003–0.027 0.024 0.012–0.059 3.2 1.0–6.1
Sertindole ≤5 Combined 0.19 0.042–0.68 0.98 0.23–3.3 5.3 4.9–8.0
Ziprasidone ≤5 Combined 0.016 0.003–0.73 0.064 0.040–0.10 7.5 0.84–16
Zuclopenthixol ≤5 Toxic 0.052 0.028–0.21 0.47 0.20–2.3 9.2 6.5–11
34 Therapeutic 0.038 0.017–0.069 0.22 0.084–0.49 6.2 3.2–10
Cardiovascular Amlodipine 6 Toxic 0.13 0.13–1.1 0.18 0.14–1.2 1.1 0.96–1.4
100 Therapeutic 0.061 0.033–0.11 0.066 0.044–0.13 1.3 0.75–2.0
Atenolol ≤5 Therapeutic 0.50 0.28–2.7 0.20 0.068–0.73 0.26 0.18–0.38
Carvedilol 21 Therapeutic 0.026 0.010–0.11 0.030 0.007–0.099 0.96 0.42–2.0
Enalaprilat ≤5 Combined 0.20 0.039-0.51 0.067 0.007-0.20 0.22 0.18-0.62
Metoprolol 9 Toxic 1.9 0.75–56 1.7 1.1–48 0.89 0.67–1.9
180 Therapeutic 0.12 0.021–0.46 0.16 0.036–0.76 1.8 0.70–3.0
Propranolol 24 Combined 0.043 0.007–0.42 0.11 0.035–1.5 5.4 2.9–8.0
Verapamil ≤5 Toxic 2.6 1.8–4.6 2.3 1.0–15 0.89 0.53–2.9
15 Therapeutic 0.16 0.037–0.32 0.093 0.021–0.40 0.47 0.30–1.6
Norverapamil ≤5 Toxic 1.2 0.42–1.8 0.47 0.21–2.8 0.63 0.44–1.5
14 Therapeutic 0.13 0.047–0.21 0.053 0.030–0.11 0.49 0.33–0.88
Opioid Buprenorphine 18 Toxic 0.002 0.0004–0.004 0.007 0.004–0.016 6.6 2.4–12
20 Therapeutic 0.0008 0.0001–0.008 0.005 0.001–0.023 7.3 2.3–20
Norbuprenorphine 7 Toxic 0.005 0.001–0.010 0.003 0.001–0.005 0.65 0.41–0.71
≤5 Therapeutic 0.013 0.007–0.014 0.005 0.0003–0.006 0.48 0.27–0.57
Codeine 16 Toxic 0.48 0.083–2.5 0.65 0.11–2.8 1.3 0.72–2.1
85 Therapeutic 0.036 0.015–0.19 0.052 0.029–0.30 1.8 0.73–2.8
Dextromethorphan 7 Combined 0.019 0.004-0.065 0.085 0.041-0.46 11 4.0-11
Fentanyl 20 Toxic 0.012 0.002–0.086 0.022 0.003–0.14 1.7 0.96–5.1
95 Therapeutic 0.004 0.001–0.023 0.011 0.003–0.064 2.8 0.85–11
Ketobemidone 9 Toxic 0.11 0.024–0.29 0.16 0.032–0.41 1.3 1.1–1.5
10 Therapeutic 0.041 0.013–0.077 0.038 0.022–0.15 1.6 0.84–2.1
Loperamide 29 Therapeutic 0.005 0.0008–0.013 0.003 0.0008–0.008 0.74 0.44–1.1
Methadone 363 Toxic 0.57 0.20–1.9 1.3 0.42–3.7 2.1 1.3–3.5
94 Therapeutic 0.19 0.045–1.1 0.40 0.097–2.3 2.0 1.3–3.9
6-MAM 22 Combined 0.017 0.006–0.098 0.090 0.033–0.33 5.5 1.2–12
Morphinea 190 Toxic 0.19 0.042–1.0 0.13 0.035–0.61 0.78 0.23–1.8
117 Therapeutic 0.072 0.017–0.35 0.059 0.027–0.24 0.91 0.37–2.9
Morphine-6-glucuronide 11 Toxic 0.32 0.14–0.86 0.11 0.031–0.20 0.23 0.16–0.97
10 Therapeutic 0.46 0.16–1.1 0.10 0.014–0.45 0.22 0.068–0.59
Naloxone 12 Therapeutic 0.008 0.004–0.025 0.016 0.008–0.031 2.2 0.48–3.8
Oxycodone 69 Toxic 0.33 0.037–2.1 0.56 0.063–2.5 1.8 0.99–2.5
112 Therapeutic 0.048 0.009–0.24 0.086 0.018–0.42 1.8 1.2–2.9
Tapentadol ≤5 Therapeutic 0.066 0.015–0.31 0.077 0.020–1.6 2.4 1.4–4.9
Tramadol 65 Toxic 2.4 0.47–13 3.4 0.64–25 1.6 0.73–2.3
106 Therapeutic 0.39 0.045–1.5 0.63 0.071–2.1 1.7 1.2–2.6
O-Desmethyltramadol 67 Toxic 0.38 0.051–1.7 0.52 0.071–2.4 1.5 1.0–1.9
75 Therapeutic 0.099 0.037–0.31 0.16 0.061–0.41 1.6 1.0–2.3
Sedative–hypnotic Alprazolama 55 Toxic 0.028 0.009–0.14 0.077 0.021–0.38 2.5 1.9–3.2
55 Therapeutic 0.016 0.003–0.041 0.039 0.010–0.096 2.6 1.8–3.2
Bromazepama 29 Toxic 0.22 0.045–0.44 0.31 0.063–0.73 1.4 1.2–1.7
35 Therapeutic 0.045 0.015–0.29 0.076 0.021–0.40 1.5 1.2–2.1
Chlordiazepoxidea 53 Toxic 0.52 0.059–2.3 0.70 0.12–3.6 1.6 1.0–2.8
96 Therapeutic 0.25 0.022–1.5 0.40 0.032–2.2 1.5 0.87–2.5
Clobazam ≤5 Therapeutic 0.017 0.010–0.041 0.041 0.021–0.082 2.0 1.9–2.3
Norclobazam ≤5 Therapeutic 0.066 0.036–0.13 0.16 0.11–0.28 2.5 2.2–3.3
Clonazepama 64 Toxic 0.005 0.002–0.022 0.033 0.013–0.099 6.6 2.6–13
43 Therapeutic 0.004 0.002–0.011 0.028 0.014–0.076 7.0 3.7–14
7-Aminoclonazepama 167 Toxic 0.15 0.027–0.48 0.11 0.023–0.32 0.74 0.54–1.1
171 Therapeutic 0.063 0.018–0.18 0.045 0.016–0.14 0.76 0.57–1.1
Demoxepam 59 Toxic 0.83 0.21–3.1 1.8 0.27–4.6 1.6 1.2–2.2
96 Therapeutic 0.57 0.23–2.2 0.91 0.36–3.9 1.5 1.1–2.1
Diazepama 59 Toxic 0.082 0.020–0.35 0.13 0.028–0.40 1.4 0.91–2.2
148 Therapeutic 0.041 0.010–0.18 0.064 0.015–0.32 1.5 0.86–3.1
N-Demethyldiazepama 110 Toxic 0.14 0.020–0.48 0.31 0.047–1.1 2.3 1.3–3.6
310 Therapeutic 0.051 0.009–0.31 0.13 0.021–0.68 2.4 1.3–3.9
Flubromazolam ≤5 Toxic 0.008 0.005–0.012 0.043 0.043–0.049 6.4 4.0–9.0
Lorazepam 17 Combined 0.017 0.004-0.096 0.058 0.017-0.30 3.5 2.3-5.6
Midazolam 65 Therapeutic 0.015 0.005–0.31 0.099 0.017–0.91 3.8 1.4–13
Nitrazepama ≤5 Toxic 0.019 0.009–0.098 0.18 0.10–0.37 9.6 5.1–12
≤5 Therapeutic 0.008 0.006–0.012 0.045 0.017–0.063 5.3 2.0–7.3
7-Aminonitrazepama 23 Toxic 0.073 0.035–0.41 0.062 0.023–0.32 0.83 0.58–0.95
36 Therapeutic 0.062 0.018–0.15 0.043 0.015–0.14 0.81 0.53–1.2
Oxazepama 45 Toxic 0.027 0.011–0.39 0.064 0.022–0.75 2.0 1.4–3.3
126 Therapeutic 0.047 0.013–0.37 0.11 0.028–0.73 2.0 1.2–3.3
Phenobarbital ≤5 Toxic 14 7.8–66 17 9.8–91 1.3 1.2–1.5
12 Therapeutic 11 6.1–22 12 7.2–29 1.2 1.1–1.4
Scopolamine ≤5 Therapeutic 0.0003 0.0003–0.0006 0.009 0.003–0.011 26 5.8–39
Temazepama 17 Toxic 0.022 0.011–0.065 0.026 0.012–0.067 1.1 0.81–2.2
24 Therapeutic 0.026 0.013–0.050 0.025 0.015–0.063 0.96 0.59–1.9
Zolpidem 7 Toxic 0.29 0.13–0.96 0.28 0.098–1.8 0.96 0.78–1.8
11 Therapeutic 0.11 0.066–0.57 0.086 0.048–0.33 0.73 0.49–1.2
Zopiclone 62 Toxic 0.18 0.030–0.83 0.28 0.031–1.2 1.4 0.80–2.1
129 Therapeutic 0.031 0.008–0.13 0.045 0.012–0.20 1.5 0.99–2.4
Stimulant Amphetaminea 50 Toxic 0.45 0.080–2.4 1.3 0.18–6.2 2.8 0.98–4.0
83 Therapeutic 0.10 0.024–0.93 0.32 0.065–2.2 3.2 1.7–4.6
Atomoxetine 8 Combined 0.098 0.037-0.36 0.73 0.21-2.4 5.9 5.0-9.3
Cocainea 76 Toxic 2.6 0.10–13 7.5 0.11–25 2.4 0.70–5.0
134 Therapeutic 0.084 0.015–0.52 0.18 0.027–0.84 2.0 0.73–4.9
Benzoylecgonine 34 Toxic 4.1 0.56–11 1.8 0.48–4.9 0.49 0.30–1.0
178 Therapeutic 0.32 0.072–1.7 0.20 0.056–0.79 0.66 0.35–1.3
Caffeine 18 Therapeutic 4.6 1.1–15 5.1 1.0–16 1.1 0.98–1.3
MDA 10 Toxic 0.064 0.017–0.13 0.19 0.043–0.45 2.9 1.9–4.5
9 Therapeutic 0.032 0.019–0.11 0.15 0.068–0.33 3.2 2.4–5.0
MDMAa 14 Toxic 1.2 0.19–4.6 4.2 0.55–23 2.6 2.0–4.8
13 Therapeutic 0.26 0.059–0.57 0.77 0.26–3.6 3.7 1.7–5.5
Methamphetamine 6 Combined 0.50 0.12–4.1 1.0 0.50–8.6 3.1 1.5–4.1
Methylphenidatea ≤5 Toxic 0.020 0.0085–0.44 0.062 0.017–0.71 2.0 1.6–3.9
44 Therapeutic 0.027 0.0073–0.21 0.058 0.015–0.37 2.6 0.91–4.0
Miscellaneous Atropine 30 Therapeutic 0.013 0.005–0.056 0.013 0.006–0.029 0.91 0.38–3.0
Baclofen 15 Combined 0.68 0.20–3.3 0.11 0.032–0.58 0.18 0.084–0.32
Biperiden 12 Therapeutic 0.010 0.001–0.034 0.012 0.005–0.038 1.4 0.62–5.2
Colchicine ≤5 Combined 0.010 0.006–0.037 0.003 0.002–0.007 0.28 0.20–0.36
Donepezil 6 Therapeutic 0.14 0.086–0.17 0.30 0.19–0.33 2.0 1.8–2.8
Ephedrinea 59 Therapeutic 0.070 0.018–0.38 0.16 0.049–0.80 2.6 1.6–4.1
Fluconazole ≤5 Therapeutic 2.3 0.34–15 1.9 0.28–11 0.82 0.73–1.0
Lamotrigine 22 Therapeutic 4.2 0.55–11 6.5 1.1–11 1.4 1.1–1.9
Levetiracetam 13 Therapeutic 9.6 1.4–19 11 1.7–26 1.2 0.91–1.7
LSD ≤5 Combined 0.001 0.0003–0.002 0.011 0.003–0.011 8.7 5.8–18
Metformin 22 Combined 3.6 1.2–28 1.0 0.31–5.6 0.28 0.062–0.56
Metoclopramide 13 Toxic 0.26 0.20–0.79 0.20 0.095–0.50 0.82 0.33–1.3
49 Therapeutic 0.12 0.015–0.35 0.071 0.013–0.21 0.76 0.34–1.3
Ondansetron 30 Therapeutic 0.030 0.014–0.065 0.054 0.021–0.14 2.1 1.0–3.1
Orphenadrine ≤5 Toxic 2.6 2.0–5.4 11 6.4–35 4.1 3.2–6.3
21 Therapeutic 0.39 0.059–1.5 1.1 0.15–3.9 3.0 2.3–4.6
N-Demethylorphenadrine 14 Combined 0.098 0.028–0.53 0.63 0.13–2.2 5.1 3.2–7.3
Sildenafil 7 Therapeutic 0.12 0.026–0.23 0.050 0.005–0.097 0.41 0.18–0.82
THC 245 Therapeutic 0.005 0.001–0.018 0.007 0.002–0.033 1.81 0.54–4.8
THC-COOH 248 Therapeutic 0.016 0.005–0.041 0.012 0.005–0.041 0.95 0.43–1.9
Topiramate ≤5 Therapeutic 8.8 2.8–13 6.3 1.7–10 0.63 0.45–0.89
Open in a new tab
a

Drugs previously published with fewer cases by the Department of Forensic Medicine [26–34].

Brain–blood ratio

The brain–blood ratio of a given drug or metabolite is affected by several factors, including lipophilicity, pKa, stability, half-life, and postmortem redistribution. Additionally, route of administration and time from consumption to death are important factors influencing the brain–blood ratio [19]. The distribution of compounds and their corresponding median brain–blood ratios within each drug group without classification into toxic or therapeutic categories is shown in Fig. 1.

Figure 1.

Scatter plot showing the median brain–blood ratios of 122 compounds grouped into nine drug classes: analgesic/anaesthetic, antihistamine, cardiovascular, stimulant, antipsychotic, miscellaneous, opioid, antidepressant, and sedative-hypnotic. The x-axis represents the brain–blood ratio, and the y-axis lists the drug classes. Each point represents a single compound. A vertical dashed line at a brain–blood ratio of 1 indicates equal concentrations in brain and blood. Most compounds have ratios between approximately 0 and 5, with considerable variability within drug classes. Antidepressants and sedative-hypnotics generally show the highest ratios, including several compounds above 10 and one sedative-hypnotic outlier near 26. Opioids and antipsychotics also include compounds with elevated ratios up to approximately 12 and 8, respectively. Cardiovascular drugs and analgesic/anaesthetics are clustered closer to or below a ratio of 2. Most compounds across all classes lie above the reference line, indicating higher concentrations in brain tissue than in blood.

Open in a new tab

Distribution of all 122 compounds, including drugs of abuse, pharmaceuticals, and metabolites, and their corresponding median brain–blood ratio grouped into 9 representative drug groups. Median brain–blood ratios are based on all cases and not divided into toxic and therapeutic categories. The dashed line (- - -) designates the distribution of brain–blood ratios above and below 1.

As seen in Fig. 1, the highest and widest distributions of median brain–blood ratios were observed for compounds primarily targeting the nervous system, especially antidepressants and sedative-hypnotics (Fig. 1). Antidepressants, antipsychotics, and stimulants all had a median brain–blood ratio above 1 except for amisulpride and the metabolite benzoylecgonine, indicating their permeability across the BBB. The detected antidepressants showed a wide range of brain–blood ratios with vortioxetine having the highest brain–blood ratio of 14 within this group. The sedative-hypnotics showed the widest range from 0.76 to 26 of median brain–blood ratios due to the high brain–blood ratio of scopolamine. The remaining sedative-hypnotics were more clustered in the lower end of the range from 0.76 to 6.7. In the analgesic/anesthetic group, ketamine was the only drug with a higher concentration in brain than blood.

Generally, the observed variation in brain–blood ratios across compounds was consistent with differences in their permeability across the BBB, influenced by lipophilicity, polarity, and volume of distribution, as well as variation in Pgp-mediated efflux at the BBB or nonspecific receptor binding of certain compounds [16, 40–46].

Metabolites

Drug metabolites may be inactive or possess similar, enhanced, or different pharmacological actions as their parent drug [47]. Differences in brain–blood ratios for parent drugs and their corresponding metabolites were observed across drugs represented in Table 1. For several drugs, the brain–blood ratios were higher than those observed for their metabolites. This was seen for, e.g. cocaine and its metabolite benzoylecgonine as well as nitrazepam and clonazepam and their corresponding 7-amino metabolites. Despite the higher ratios for the parent drugs, both benzoylecgonine and the 7-amino metabolites exhibited higher median concentration in both blood and brain than their respective parent drugs. The higher concentration of 7-amino metabolites compared to parent compound has previously been reported in blood, pericardial fluid, muscle, and vitreous humor [1, 48]. A similar difference in brain–blood ratio was observed for buprenorphine, citalopram, hydroxyzine, and their metabolites, where the median brain–blood ratios of the parent drug were up to 10 times higher than the median brain–blood ratio of active metabolite. In contrast, clomipramine, imipramine, and fluoxetine exhibited lower median brain–blood ratios than their metabolites N-demethylclomipramine, N-demethylimipramine, and norfluoxetine. However, these findings were based on a limited number of cases in each category.

Differences in brain–blood ratios could be explained by differences in physicochemical properties of the compounds, BBB permeability, metabolism and elimination kinetics, and postmortem changes [49, 50]. Higher concentrations of the parent drug relative to its metabolite might indicate a recent exposure and limited metabolic conversion, whereas higher concentrations of the metabolite may be consistent with a longer interval between drug intake and death [50]. Nevertheless, the parent drug-metabolite ratio is not a specific indicator of the time since drug intake, as it may also be influenced by metabolite accumulation during repeated exposure, differences in elimination rates, and postmortem conversion or degradation of the parent drug through bacterial or enzymatic activity [49, 50]. Therefore, the parent drug-metabolite ratio should be interpreted with caution in the context of drug pharmacokinetics and case-specific information.

Interpretive considerations in postmortem toxicology

The interpretation of postmortem drug concentrations and their contribution to the cause of death is a complex task that depends on multiple physiological, environmental, pharmacological, and postmortem factors [51–53]. Therefore, a drug concentration measured after death may not necessarily reflect the concentration at time of death [5, 52–57].

One major limitation is that drug concentrations can continue to change after death due to ongoing postmortem processes. As the postmortem interval increases, biochemical and structural changes in tissues may affect drug stability and distribution within the body [2, 58]. Some compounds are prone to postmortem degradation, including chemical, enzymatic, or bacterial degradation [59]. For unstable compounds, this process can lead to a reduction in detectable parent drug concentrations or in some cases, formation of metabolites or other degradation products that complicate interpretation. This is particularly relevant for compounds such as cocaine, olanzapine, and nitrobenzodiazepines [49, 55, 60]. Simultaneously, postmortem redistribution may occur, whereby concentration gradients between tissues and blood may lead to passive diffusion of compounds, often resulting in elevated concentrations in central blood compared to peripheral sites, thereby affecting the brain–blood ratio [5, 57, 61]. Compounds with high lipophilicity, large volumes of distribution, or basic properties are particularly prone to postmortem redistribution [2, 62]. Therefore, the anatomical site of sampling must be carefully considered when interpreting toxicological results [59, 62].

Even when postmortem changes are limited, the relationship between drug concentration and toxicity is rarely straightforward. Concentrations considered toxic in drug-naïve individuals may be within the therapeutic range in habitual users due to tolerance development associated with chronic drug use, as seen for opioids and stimulants [4, 63]. For example, habitual users and individuals using methadone for maintenance therapy or with a history of addiction may develop a higher tolerance than naïve recreational users [64]. Consequently, lower doses can be fatal in cases of non-habitual use causing overlapping postmortem methadone concentrations between fatal cases and habitual users, especially when combined with other drugs [64]. Combined drug effects may be additive or synergistic, particularly when CNS depressants are involved [52, 65]. These interactions may result in fatal outcomes even when individual drug concentrations fall within therapeutic or sub-toxic ranges. Additionally, underlying diseases or pathological conditions such as cardiovascular disease, respiratory disorders, or hepatic impairment may increase susceptibility to drug toxicity or contribute directly to death. In such cases, the cause of death may involve a complex interplay between toxicological and natural factors [52]. Therefore, interpretation of postmortem drug concentrations requires particular caution for compounds associated with tolerance development or additive effects. Measured concentrations should be interpreted in conjunction with other toxicological findings, as well as information from the autopsy report and relevant circumstantial data [50].

In summary, postmortem drug concentrations and consequently the brain–blood ratios, are affected by multiple factors, including the timing of drug intake relative to death, the postmortem interval, postmortem degradation, and the extent of postmortem redistribution. These factors must be considered alongside interindividual variability in drug tolerance and the potential additive or synergistic effects of co-occurring compounds. By providing new reference concentrations and brain–blood ratios, this study strengthens the framework for future toxicological interpretation of the cause of death.

Conclusion

The present study reports toxic and therapeutic postmortem brain concentrations and brain–blood ratios for 122 drugs of abuse, pharmaceuticals, and metabolites frequently encountered in forensic autopsy cases. For the majority of the compounds, brain concentration exceeded those in blood, consistent with expectations for compounds that act on the CNS. The reported brain concentrations and brain–blood ratios may serve as reference values for the interpretation of toxicological findings in future forensic death investigations, when brain tissue is used as a supplementary matrix or when blood is unavailable for analysis.

Contributor Information

Kathrine Østerballe Skov, Section of Forensic Chemistry, Department of Forensic Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.

Mikayla Zoë van der Meer, Section of Forensic Chemistry, Department of Forensic Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.

Michael Nedahl, Section of Forensic Chemistry, Department of Forensic Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.

Marie Katrine Klose Nielsen, Section of Forensic Chemistry, Department of Forensic Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.

Author contributions

Kathrine Østerballe Skov (Conceptualization, Formal analysis, Methodology, Visualization, Investigation, Writing—original draft, Writing—review & Editing), Mikayla van der Meer (Conceptualization, Methodology, Validation, Visualization, Writing—review & editing), Michael Nedahl (Conceptualization, Methodology, Supervision, Validation, Visualization, Writing—review & editing), and Marie Katrine Klose Nielsen (Conceptualization, Methodology, Supervision, Validation, Investigation, Visualization, Writing—review & editing)

Conflicts of interest

None of the authors have any conflicts of interest concerning this study to disclose.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or nonprofit sectors.

Data Availability

The data underlying this article cannot be shared publicly due to the nature of the study, which involves retrospective analysis of postmortem material collected from routine cases. Data sharing is limited to protect confidentiality and is per institutional guidelines.

Ethics statement

This was a retrospective study based on pseudonymized data from January 2014 to March 2025. Results are shown in an aggregated form, and all data management was approved by the University of Copenhagen on behalf of the Danish Data Protection Agency in accordance with the European General Data Protection Regulation (Regulation number 2016/697, Journal number: 514-0928/24-3000).

References

  • 1. Ketola RA, Ojanperä I.  Summary statistics for drug concentrations in post-mortem femoral blood representing all causes of death. Drug Test Anal  2019;11:1326–37. 10.1002/dta.2655 [DOI] [PubMed] [Google Scholar]
  • 2. Abdelaal GMM, Hegazy NI, Etewa RL  et al.  Postmortem redistribution of drugs: a literature review. Forensic Sci Med Pathol  2023;20:1483–90. 10.1007/s12024-023-00709-z [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3. Peters FT, Steuer AE.  Antemortem and postmortem influences on drug concentrations and metabolite patterns in postmortem specimens. WIREs Forensic Sci  2019;1:1–21. 10.1002/wfs2.1297 [DOI] [Google Scholar]
  • 4. Linnet K.  Postmortem drug concentration intervals for the non-intoxicated state – a review. J Forensic Leg Med  2012;19:245–9. 10.1016/j.jflm.2012.02.010 [DOI] [PubMed] [Google Scholar]
  • 5. Pounder DJ, Jones GR.  Post-mortem drug redistribution–a toxicological nightmare. Forensic Sci Int  1990;45:253–63. 10.1016/0379-0738(90)90182-X [DOI] [PubMed] [Google Scholar]
  • 6. Rohrig TP, Hicks CA.  Brain tissue: a viable postmortem toxicological specimen. J Anal Toxicol  2015;39:137–9. 10.1093/jat/bku139 [DOI] [PubMed] [Google Scholar]
  • 7. Øiestad AML, Karinen R, Rogde S  et al.  Comparative study of postmortem concentrations of antidepressants in several different matrices. J Anal Toxicol  2018;42:446–58. 10.1093/jat/bky030 [DOI] [PubMed] [Google Scholar]
  • 8. de Campos EG, da Costa BRB, dos Santos FS  et al.  Alternative matrices in forensic toxicology: a critical review. Forensic Toxicol  2022;40:1–18. 10.1007/s11419-021-00596-5 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9. Hansen SL, Dalsgaard PW, Linnet K  et al.  Comparison of comprehensive screening results in postmortem blood and brain tissue by UHPLC–QTOF-MS. J Anal Toxicol  2022;46:1053–8. 10.1093/jat/bkac011 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10. Hansen SL, Nielsen MKK, Linnet K  et al.  Suitability of cardiac blood, brain tissue, and muscle tissue as alternative matrices for toxicological evaluation in postmortem cases. Drug Test Anal  2023;15:529–38. 10.1002/dta.3439 [DOI] [PubMed] [Google Scholar]
  • 11. Behnke G, Gray TR, Arndt C.  Brain homogenate stability for stimulant drugs. J Anal Toxicol  2024;48:514–8. 10.1093/jat/bkae058 [DOI] [PubMed] [Google Scholar]
  • 12. Stimpfl T, Reichel S.  Distribution of drugs of abuse within specific regions of the human brain. Forensic Sci Int  2007;170:179–82. 10.1016/j.forsciint.2007.03.032 [DOI] [PubMed] [Google Scholar]
  • 13. Hammarlund-Udenaes M, Loryan I.  Assessing central nervous system drug delivery. Expert Opin Drug Deliv  2025;22:421–39. 10.1080/17425247.2025.2462767 [DOI] [PubMed] [Google Scholar]
  • 14. Abbott NJ, Patabendige AAK, Dolman DEM  et al.  Structure and function of the blood-brain barrier. Neurobiol Dis  2010;37:13–25. 10.1016/j.nbd.2009.07.030 [DOI] [PubMed] [Google Scholar]
  • 15. Kulkarni AD, Patel HM, Surana SJ  et al.  Brain-blood ratio: Implications in brain drug delivery. Expert Opin Drug Deliv  2016;13:85–92. 10.1517/17425247.2016.1092519 [DOI] [PubMed] [Google Scholar]
  • 16. Obradovic T, Dobson GG, Shingaki T  et al.  Assessment of the first and second generation antihistamines brain penetration and role of P-glycoprotein. Pharm Res  2007;24:318–27. 10.1007/s11095-006-9149-4 [DOI] [PubMed] [Google Scholar]
  • 17. Dauchy S, Dutheil F, Weaver RJ  et al.  ABC transporters, cytochromes P450 and their main transcription factors: expression at the human blood-brain barrier. J Neurochem  2008;107:1518–28. 10.1111/j.1471-4159.2008.05720.x [DOI] [PubMed] [Google Scholar]
  • 18. Pardridge WM.  Drug transport across the blood-brain barrier. J Cereb Blood Flow Metab  2012;32:1959–72. 10.1038/jcbfm.2012.126 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19. Summerfield SG, Read K, Begley DJ  et al.  Central nervous system drug disposition: The relationship between in situ brain permeability and brain free fraction. J Pharmacol Exp Ther  2007;322:205–13. 10.1124/jpet.107.121525 [DOI] [PubMed] [Google Scholar]
  • 20. Schulz M, Schmoldt A, Andresen-Streichert H  et al.  Revisited: Therapeutic and toxic blood concentrations of more than 1100 drugs and other xenobiotics. Crit Care  2020;24:195. 10.1186/s13054-020-02915-5 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 21. Jones AW, Holmgren A, Ahlner J.  Post-mortem concentrations of drugs determined in femoral blood in single-drug fatalities compared with multi-drug poisoning deaths. Forensic Sci Int  2016;267:96–103. 10.1016/j.forsciint.2016.08.015 [DOI] [PubMed] [Google Scholar]
  • 22. Reis M, Aamo T, Ahlner J  et al.  Reference concentrations of antidepressants. A compilation of postmortem and therapeutic levels. J Anal Toxicol  2007;31:254–64. 10.1093/jat/31.5.254 [DOI] [PubMed] [Google Scholar]
  • 23. Kriikku P, Ojanperä I.  Fatal concentrations of antidepressant and antipsychotic drugs in postmortem femoral blood. J Anal Toxicol  2023;47:615–22. 10.1093/jat/bkad044 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24. Söderberg C, Wernvik E, Tillmar A  et al.  Antipsychotics – Postmortem fatal and non-fatal reference concentrations. Forensic Sci Int  2016;266:91–101. 10.1016/j.forsciint.2016.05.002 [DOI] [PubMed] [Google Scholar]
  • 25. Jönsson AK, Söderberg C, Espnes KA  et al.  Sedative and hypnotic drugs-Fatal and non-fatal reference blood concentrations. Forensic Sci Int  2014;236:138. 10.1016/j.forsciint.2014.01.005 [DOI] [PubMed] [Google Scholar]
  • 26. van der Meer MZ , Rasmussen BS, Nedahl M  et al.  Brain concentrations and brain–blood ratios of amitriptyline and nortriptyline in forensic postmortem cases. J Anal Toxicol  2025;49:209–15. 10.1093/jat/bkaf017 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 27. Nedahl M, Johansen SS, Linnet K.  Postmortem brain-blood ratios of codeine, fentanyl, oxycodone and tramadol. J Anal Toxicol  2021;45:53–9. 10.1093/jat/bkaa048 [DOI] [PubMed] [Google Scholar]
  • 28. Nedahl M, Johansen SS, Linnet K.  Postmortem brain-blood ratios of amphetamine, cocaine, ephedrine, mdma and methylphenidate. J Anal Toxicol  2019;43:378–84. 10.1093/jat/bky110 [DOI] [PubMed] [Google Scholar]
  • 29. Nedahl M, Johansen SS, Linnet K.  Brain-blood ratio of morphine in heroin and morphine autopsy cases. Forensic Sci Int  2019;301:388–93. 10.1016/j.forsciint.2019.06.007 [DOI] [PubMed] [Google Scholar]
  • 30. Skov L, Holm KMD, Johansen SS  et al.  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. 10.1093/jat/bkw059 [DOI] [PubMed] [Google Scholar]
  • 31. Nedahl M, Johansen S, Linnet K.  Reference brain and blood concentrations of olanzapine in postmortem cases. J Anal Toxicol  2018;42:650–4. 10.1093/jat/bky036 [DOI] [PubMed] [Google Scholar]
  • 32. Nedahl M, Johansen SS, Linnet K.  Reference brain/blood concentrations of citalopram, duloxetine, mirtazapine and sertraline. J Anal Toxicol  2018;42:149–56. 10.1093/jat/bkx098 [DOI] [PubMed] [Google Scholar]
  • 33. Skov L, Holm KMD, Linnet K.  Nitrobenzodiazepines: postmortem brain and blood reference concentrations. Forensic Sci Int  2016;268:39–45. 10.1016/j.forsciint.2016.09.002 [DOI] [PubMed] [Google Scholar]
  • 34. Skov L, Johansen SS, Linnet K.  Postmortem quetiapine reference concentrations in brain and blood. J Anal Toxicol  2015;39:557–61. 10.1093/jat/bkv072 [DOI] [PubMed] [Google Scholar]
  • 35. Wille SMR, De Letter EA, Piette MHA  et al.  Determination of antidepressants in human postmortem blood, brain tissue, and hair using gas chromatography-mass spectrometry. Int J Legal Med  2009;123:451–8. 10.1007/s00414-008-0287-6 [DOI] [PubMed] [Google Scholar]
  • 36. Frost J, Løkken TN, Helland A  et al.  Post-mortem levels and tissue distribution of codeine, codeine-6-glucuronide, norcodeine, morphine and morphine glucuronides in a series of codeine-related deaths. Forensic Sci Int  2016;262:128–37. 10.1016/j.forsciint.2016.02.051 [DOI] [PubMed] [Google Scholar]
  • 37. van der Meer MZ, Rasmussen BS, Nedahl M, et al.  From blood to brain: postmortem brain concentrations and brain-blood ratios of chlorprothixene, clozapine, olanzapine, and quetiapine. J Anal Toxicol  2026;50:1–10. 10.1093/jat/bkag065 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 38. Nielsen MKK, Nedahl M, Johansen SS  et al.  Validation of a fully automated solid-phase extraction and ultra-high-performance liquid chromatography–tandem mass spectrometry method for quantification of 30 pharmaceuticals and metabolites in post-mortem blood and brain samples. Drug Test Anal  2018;10:1147–57. 10.1002/dta.2359 [DOI] [PubMed] [Google Scholar]
  • 39. Rygaard K, Pan M, Nielsen M, et al.  Overview of systematic toxicological analysis strategies and their coverage of substances in forensic toxicology. Anal Sci Adv  2023;4:1–8. 10.1002/ansa.202200062 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 40. Peltoniemi MA, Hagelberg NM, Olkkola KT  et al.  Ketamine: a review of clinical pharmacokinetics and pharmacodynamics in anesthesia and pain therapy. Clin Pharmacokinet  2016;55:1059–77. 10.1007/s40262-016-0383-6 [DOI] [PubMed] [Google Scholar]
  • 41. Ansotegui IJ, Bousquet J, Canonica GW  et al.  Why fexofenadine is considered as a truly non-sedating antihistamine with no brain penetration: a systematic review. Curr Med Res Opin  2024;40:1297–309. 10.1080/03007995.2024.2378172 [DOI] [PubMed] [Google Scholar]
  • 42. Katselou M, Papoutsis I, Nikolaou P, et al.  Bioanalysis of antihistamines for clinical or forensic purposes. Biomed Chromatogr  2017;31:UNSP e3727. 10.1002/bmc.3727 [DOI] [PubMed] [Google Scholar]
  • 43. McDonald K, Trick L, Boyle J.  Sedation and antihistamines: an update. Review of inter-drug differences using proportional impairment ratios. Human Psychopharmacol  2008;23:555–70. 10.1002/hup.962 [DOI] [PubMed] [Google Scholar]
  • 44. Yanai K, Ryu JH, Watanabe T  et al.  Histamine H receptor occupancy in human brains after single oral doses of histamine H antagonists measured by positron emission tomography. Br J Pharmacol  1995;116:1649–55. 10.1111/j.1476-5381.1995.tb16386.x [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 45. ter Laak AM, Bijloo GJ, Fischer M  et al.  Serum protein binding of histamine H1-antagonists. A comparative study on the serum protein binding of a sedating ([3H]mepyramine) and a non-sedating H1-antagonist ([3H]loratadine). European Journal of Pharmaceutical Sciences  1996;4:307–19. 10.1016/0928-0987(96)00172-8 [DOI] [Google Scholar]
  • 46. ter Laak AM, Tsai RS, Donne-Op Den Kelder GM, et al.  Lipophilicity and hydrogen-bonding capacity of Hi-antihistaminic agents in relation to their central sedative side-effects. Eur J Pharm Soc  1994;2:373–84. 10.1016/0928-0987(94)00065-4 [DOI] [Google Scholar]
  • 47. Hiemke C, Bergemann N, Clement HW  et al.  Consensus guidelines for therapeutic drug monitoring in neuropsychopharmacology: update 2017. Pharmacopsychiatry  2018;51:9–62. 10.1055/s-0043-116492 [DOI] [PubMed] [Google Scholar]
  • 48. Øiestad EL, Øiestad ÅML, Middelkoop G  et al.  Comparative study of postmortem concentrations of benzodiazepines and Z-hypnotics in several different matrices. J Anal Toxicol  2023;47:287–98. 10.1093/jat/bkac106 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 49. Robertsen MD, Drummer OH.  Postmortem drug metabolism by bacteria. J Forensic Sci  1995;40:382–6. [PubMed] [Google Scholar]
  • 50. Stephens BG, Jentzen JM, Karch S  et al.  Criteria for the interpretation of cocaine levels in human biological samples and their relation to the cause of death. Am J Forensic Med Pathol  2004;25:1–10. 10.1097/01.paf.0000118960.58334.a9 [DOI] [PubMed] [Google Scholar]
  • 51. Pélissier-Alicot AL, Gaulier JM, Champsaur P  et al.  Mechanisms underlying postmortem redistribution of drugs: a review. J Anal Toxicol  2003;27:533–44. 10.1093/jat/27.8.533 [DOI] [PubMed] [Google Scholar]
  • 52. Stephenson L, Van Den Heuvel C, Scott T  et al.  Difficulties associated with the interpretation of postmortem toxicology. Journal of Analytical Toxicology  2024;48:405–12. 10.1093/jat/bkae052 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 53. Gleba J, Kim J.  A mechanism-based forensic investigation into the postmortem redistribution of morphine. J Anal Toxicol  2020;44:256–62. 10.1093/jat/bkz093 [DOI] [PubMed] [Google Scholar]
  • 54. Staeheli SN, Gascho D, Ebert LC  et al.  Time-dependent postmortem redistribution of morphine and its metabolites in blood and alternative matrices—application of CT-guided biopsy sampling. Int J Legal Med  2017;131:379–89. 10.1007/s00414-016-1485-2 [DOI] [PubMed] [Google Scholar]
  • 55. Saar E, Beyer J, Gerostamoulos D  et al.  The time-dependant post-mortem redistribution of antipsychotic drugs. Forensic Sci Int  2012;222:223–7. 10.1016/j.forsciint.2012.05.028 [DOI] [PubMed] [Google Scholar]
  • 56. Mantinieks D, Gerostamoulos D, Glowacki L  et al.  Postmortem drug redistribution: a compilation of postmortem/antemortem drug concentration ratios. J Anal Toxicol  2021;45:368–77. 10.1093/jat/bkaa107 [DOI] [PubMed] [Google Scholar]
  • 57. Borra LCP, van der Hulst R, Elsinga PH  et al.  50 Years of postmortem redistribution research: What have we learned?. Forensic Sci Int  2026;378:112699. 10.1016/j.forsciint.2025.112699 [DOI] [PubMed] [Google Scholar]
  • 58. Brockbals L, Staeheli SN, Gascho D  et al.  Time- and site-dependent postmortem redistribution of antidepressants and neuroleptics in blood and alternative matrices. J Anal Toxicol  2021;45:356–67. 10.1093/jat/bkaa092 [DOI] [PubMed] [Google Scholar]
  • 59. Leikin JB, Watson WA.  Post-mortem toxicology: what the dead can and cannot tell us. J Toxicol Clin Toxicol  2003;41:47–56. 10.1081/CLT-120018270 [DOI] [PubMed] [Google Scholar]
  • 60. Peters FT.  Stability of analytes in biosamples-an important issue in clinical and forensic toxicology?  Anal Bioanal Chem  2007;388:1505–19. 10.1007/s00216-007-1267-2 [DOI] [PubMed] [Google Scholar]
  • 61. Gerostamoulos D, Beyer J, Staikos V  et al.  The effect of the postmortem interval on the redistribution of drugs: a comparison of mortuary admission and autopsy blood specimens. Forensic Sci Med Pathol  2012;8:373–9. 10.1007/s12024-012-9341-2 [DOI] [PubMed] [Google Scholar]
  • 62. Yarema MC, Becker CE.  Key concepts in postmortem drug redistribution. Clin Toxicol  2005;43:235–41. 10.1081/CLT-58950 [DOI] [PubMed] [Google Scholar]
  • 63. Karch SB.  Alternate strategies for postmortem drug testing. J Anal Toxicol  2001;25:393–5. 10.1093/jat/25.5.393 [DOI] [PubMed] [Google Scholar]
  • 64. Pelletti G, Giunchi V, Fais P  et al.  Characterizing post-mortem blood concentrations in methadone-related deaths. Int J Legal Med  2026;140:207–16. 10.1007/s00414-025-03620-0 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 65. Wille SMR, Elliott S.  The future of analytical and interpretative toxicology: where are we going and how do we get there?  J Anal Toxicol  2021;45:619–32. 10.1093/jat/bkaa133 [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The data underlying this article cannot be shared publicly due to the nature of the study, which involves retrospective analysis of postmortem material collected from routine cases. Data sharing is limited to protect confidentiality and is per institutional guidelines.

Articles from Journal of Analytical Toxicology are provided here courtesy of Oxford University Press

RESOURCES