FORENSIC TOXICOLOGY - Bio Medical Forensics

Gamma - Hydroxybutyrate Closely
Resembles That of Ethanol
A.W. Jones, PhD, DSc*, National Lab Forensic Chemistry,
12 Artillerigatan, Linkoping, 58133, SWEDEN
After attending this presentation, attendees learn about the clinical
and forensic toxicology of two widely used recreational drugs, namely
the legal drug ethanol and the illicit drug gamma-hydroxybutyrate
(GHB). Both substances are highly soluble in water have low molecular
weight and their pharmacological effects are similar to the major central
nervous system depressants (general anesthetic gases, barbiturates and
benzodiazepines).
This presentation will impact the forensic community by teaching
the similarities and differences in clinical pharmacokinetics of ethanol
and GHB, the analysis and stability of these substances in blood during
storage, the distribution between serum and whole blood, and the effects
of food and gender on concentration-time profiles. Moreover, the
toxicity of ethanol and GHB are compared and contrasted based on the
concentrations determined in blood from impaired drivers and medical
examiner cases.
Ethanol and GHB are produced naturally in the body and are
measurable in blood and urine at very low concentrations of ~1 mg/L.
For recreational purposes both drugs are taken orally and are rapidly
absorbed from the gut and distributed into the total body water (TBW)
compartment. The distribution of ethanol and GHB between the plasma
and erythrocyte fractions of whole blood is similar to that of water
distribution, suggesting serum/whole blood ratios of 1.15:1 (range 1.10
to 1.20). Ethanol and GHB don’t bind to plasma proteins and undergo
extensive hepatic metabolism with only a small fraction (2-5%) of the
dose being recoverable in the urine. The metabolism of ethanol and
GHB occur by capacity limited kinetics and mathematically this can best
be described by the Michaelis-Menten equation. Human dosing studies
have shown that when the concentrations in blood pass 150 mg/L
(ethanol) and 10 mg/L (GHB), the metabolizing enzymes are virtually
saturated with substrate and zero-order kinetics applies. After moderate
doses, the elimination rate of ethanol from blood is within the range 100-
200 mg/L/h compared with 10-20 mg/L/h for GHB. The terminal halflives
of ethanol and GHB are relatively short; being in the range 15-30
min. The apparent volumes of distribution (V d ) of both substances are
0.5-0.7 L/kg as expected for water-soluble, non-protein bound drugs that
distribute into the TBW. Concentration-time profiles of ethanol and
GHB after moderate doses were similar for men and women in terms of
C max , t max and area under the curve (AUC). The rate and extent of
absorption is slowed considerably if ethanol or GHB are ingested
together with or after a meal, owing to delayed gastric emptying and
first-pass metabolism. Under these conditions, C max , t max and AUC
are markedly diminished compared with the same dose of the drugs
taken on an empty stomach.
Both ethanol and GHB can be determined in blood and urine by
conventional gas-liquid chromatography with a flame ionization
detector, either by direct injection or headspace technique. Methods are
also available for analysis of these substances by GC-MS, which permits
use of deuterium labeled analogues as internal standards for unequivocal
identification. The concentrations of ethanol and GHB in specimens of
whole blood from impaired drivers were remarkably stable during
storage at 4 o C for several months after sampling.
The mean and median blood-ethanol concentrations in impaired
drivers were 1,700 mg/L (N = 29,000) and in some instances the
concentrations exceeded 4000 mg/L. These results can be compared
with mean and median GHB concentrations of 89 and 82 mg/L (N = 548)
in impaired drivers, highest 340 mg/L. The concentrations of ethanol
and GHB in blood from living subjects overlapped with concentrations
seen in drug-related deaths. The mean and median blood-ethanol
concentration (N = 800) was 3600 mg/L and 3500 mg/L, respectively
compared with mean and median GHB (N = 37) of 294 mg/L and 190
mg/L, respectively.
Capacity limited pharmacokinetics of ethanol and GHB needs to be
carefully considered when the concentrations in blood after toxic doses
are interpreted. The terminal half-life should not be used to make
predictions about times necessary to eliminate ethanol or GHB from
blood or the amount ingested after large recreational or abuse doses are
taken. Interpreting the concentration of ethanol and GHB in medical
examiner in terms of toxicity and whether drug intoxication was a
possible cause of death is complicated by concomitant use of other
psychoactive substances.
Ethanol, GHB, Toxicology
K41 Determining Concentrations of Fentanyl in
Decomposing and (Formalin-Stored)
Postmortem Liver Tissue Over Time by
Gas Chromatography-Mass Spectrometry
(GC-MS)
Tiffany L. Eckert-Lumsdon, MS*, Johnson County Sheriffs Crime Lab,
6000 Lamar, Mission, KS 66202; and Jim Mcgill, PhD, Southeast
Missouri State University, One University Plaza, Cape Girardeau, MO
63701
After attending this presentation, attendees will have an overview of
the opioid analgesic drug fentanyl, its stability over time in aqueous and
liver matrices, and the effects of simulated embalming in formalin on its
concentration.
This presentation will impact the forensic community by aiding the
forensic medical examiner and forensic scientist in the determination of
fentanyl concentrations in decomposing tissue cases as well as cases
where tissue has been stored in formalin.
A systematic study of matrix effects on the postmortem
concentration of the opioid analgesic drug fentanyl in liver tissue was
conducted over a six-year period. Porcine liver homogenates were
spiked with 200 nanograms of fentanyl per gram of liver to simulate a
fatal overdose and treated with the chemical preservative formalin to
simulate embalming of the deceased victim. The samples were prepared
in triplicate (samples 1A-1C) and stored at room temperature.
Periodically, aliquots were removed from the sample containers and
extracted using a solid-phase extraction (SPE) method, and the
concentration of fentanyl was monitored over time by gas
chromatography-mass spectrometry (GC-MS). To isolate the effects of
formalin and of the liver tissue itself on fentanyl’s concentration,
triplicate samples were also prepared in which these two components
were systematically omitted from the sample sets (samples 2A-4C).
Also, negative controls were prepared in which no fentanyl was spiked
into the samples (samples 5A-6C). Statistical analysis of the
concentration data over time was conducted to determine effects of time
and other sample matrix components on fentanyl concentrations. Details
of the study, data analysis, and results as well as implications for forensic
toxicology practice will be presented.
Fentanyl, GC-MS, Solid-Phase Extraction, Formalin
75 * Presenting Author