Nitrobenzodiazepines: Postmortem brain and blood reference concentrations.

Reference concentrations are needed to evaluate postmortem toxicology results and usually femoral blood is the specimen of choice. However, brain tissue has been suggested as a viable alternative specimen, since postmortem blood concentrations can be difficult to interpret due to postmortem redistribution, among other factors. Here we present reference concentrations of postmortem brain and femoral blood of the nitrobenzodiazepines clonazepam, flunitrazepam, and nitrazepam that are of particular interest since they commonly are converted to their corresponding 7-aminometabolites in the postmortem situation. The drugs and metabolites were quantified in both matrices using LC-MS-MS in 69 cases. In 63 cases the compounds were judged not to have been of significance for the death (C cases), whereas they were considered to have been a contributing factor in 6 cases (B cases). No cases were observed with a nitrobenzodiazepine being the sole cause of death (A cases). The brain-blood ratios for clonazepam and nitrazepam were 5.5 and 4.7, respectively, while the brain-blood ratios for the 7-aminometabolites ranged from 0.4 to 0.5. Flunitrazepam only occurred as the 7-aminometabolite. A positive correlation between brain and blood concentrations was found with Spearman's rank correlation coefficients (rs) ranging from 0.77 to 0.96. The measured femoral blood concentrations agree with literature values, but only few brain concentrations were available for comparison. The drug-metabolite ratios for clonazepam and nitrazepam were 10-12 times higher in brain than in blood. The pre-analytical variation in brain of 5.9% was fairly low, suggesting that brain tissue is a useful alternative to blood. The reported brain and femoral blood concentrations serve as reference values in postmortem investigations.

Postmortem Brain and Blood Reference Concentrations of Alprazolam, Bromazepam, Chlordiazepoxide, Diazepam, and their Metabolites and a Review of the Literature.

To interpret postmortem toxicology results, reference concentrations for non-toxic and toxic levels are needed. Usually, measurements are performed in blood, but because of postmortem redistribution phenomena this may not be optimal. Rather, measurement in the target organ of psychoactive drugs, the brain, might be considered. Here we present reference concentrations of femoral blood and brain tissue of selected benzodiazepines (BZDs). Using LC-MS/MS, we quantified alprazolam, bromazepam, chlordiazepoxide, diazepam, and the metabolites desmethyldiazepam, oxazepam and temazepam in postmortem femoral blood and brain tissue in 104 cases. BZDs were judged to be unrelated to the cause of death in 88 cases and contributing to death in 16 cases. No cases were found with cause of death solely attributed to BZD poisoning. All BZDs investigated tended to have higher concentrations in brain than in blood with median brain-blood ratios ranging from 1.1 to 2.3. A positive correlation between brain and blood concentrations was found with R(2) values from 0.51 to 0.95. Our reported femoral blood concentrations concur with literature values, but sparse information on brain concentration was available. Drug-metabolite ratios were similar in brain and blood for most compounds. Duplicate measurements of brain samples showed that the pre-analytical variation in brain (5.9%) was relatively low, supporting the notion that brain tissue is a suitable postmortem specimen. The reported concentrations in both brain and blood can be used as reference values when evaluating postmortem cases.

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

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

Chiral analysis of methadone and its main metabolite, EDDP, in postmortem brain and blood by automated SPE and liquid chromatography-mass spectrometry.

We developed a method based on liquid chromatography coupled with tandem mass spectrometry to quantify individual enantiomers of methadone and its primary metabolite, R/S-2-ethyl-1,5-dimethyl-3,3-diphenylpyrrolinium (EDDP), in postmortem blood and brain tissue. Samples were prepared with a Tecan Evo robotic system. Precipitation was followed by solid-phase extraction, evaporation and reconstitution in the mobile phase. Enantiomers were fully separated with liquid chromatography on a chiral α(1)-acid glycoprotein column. A Quattro micro mass spectrometer was used for detection in the positive ion mode with an electrospray source. The lower limit of quantification in brain tissue was 0.005 mg/kg for methadone and 0.001 mg/kg for EDDP enantiomers; the maximum precision was 17% for both compounds; accuracy ranged from 94 to 101%. In blood, the limit of quantification was 0.001 mg/kg for all compounds, the total relative standard deviation was <15%, and the accuracy varied from 95 to 109%. Brain (n = 11) and blood (n = 15) samples were analyzed with intermediate precision that varied from 7.5 to 15% at 0.005 mg/kg and from 6.8 to 11.3% at 0.25 mg/kg for all compounds. Method development focused on producing a clean extract, particularly from brain samples. The method was tested on authentic brain and femoral blood samples.

Determination of ketone bodies in blood by headspace gas chromatography-mass spectrometry.

A gas chromatography-mass spectrometry (GC-MS) method for determination of ketone bodies (ß-hydroxybutyrate, acetone, and acetoacetate) in blood is presented. The method is based on enzymatic oxidation of D-ß-hydroxybutyrate to acetoacetate, followed by decarboxylation to acetone, which was quantified by the use of headspace GC-MS using acetone-(13)C(3) as an internal standard. The developed method was found to have intra- and total interday relative standard deviations < 10% for acetone+acetoacetate levels (∼25 to 8300 µM) and D-ß-hydroxybutyrate levels (∼30 to 16500 µM). Recovery values varied from 98 to 107%, demonstrating the suitability of the method for measuring ketone bodies over a wide concentration range. The method has been applied to cases in which ketoacidosis was suspected as the cause of death in diabetics or chronic alcoholics, as well as to cases in which another cause of death was identified.