PostMortem Drug Changes

1
Post-Mortem Drug Changes

• Prof. Dr. Olaf H. Drummer
• Monash University, Melbourne
• AUSTRALIA
• olaf_at_vifm.org

2
Introduction

• Within minutes of death a number of processes
  occur that can significantly affect
  concentrations of drugs
• Lividity and partitioning of fluids
• Redistribution
• Metabolism
• Stability-induced changes
• These changes must be understood in order to
  interpret post-mortem toxicology

3
Alcohol Production (CH3CH2OH)

• Ethanol is produced after death
• By fermentation!
• Requires glucose or other substrates
• Rate variable and depends on
• Ambient temperature
• Time hours to days
• Presence of appropriate bacteria
• Extent of formation of alcohol?
• Up to at least 0.2 (gram/100 mL)
• Suggest collection of vitreous humour, or urine
• Should be similar to BAC, or slightly higher

4
Vitreous Humour

• This fluid is very easy to work with since it is
  watery and dose not produce matrix effects
• Generally limited to assisting in the
  interpretation of blood alcohol data
• gives very similar concentrations to blood
• Useful tissue for biochemistries
• glucose
• urea
• electrolytes
• Many drugs have similar concentrations in
  vitreous to blood

5
Examples

• In a normal body
• Blood alcohol 0.14
• Vitreous alcohol 0.15
• Alcohol is probably real
• In a decomposed body
• Blood alcohol 0.08
• Vitreous alcohol 0.01
• Alcohol probably all by fermentation

6
Hydrogen Cyanide (HCN)

• Hydrogen cyanide is a poisonous substance
• Derives from cyanide salts
• Emissions from fires burning plastics etc
• Cyanide is produced after death
• by cyanogenic bacteria
• Ensure blood contains preservative, or better, is
  frozen at -20 C or less.
• HCN if present in specimens is volatile
  (unstable) and will dissipate with time, even if
  specimen is frozen

7
Examples

• In fire death
• CO 35
• Cyanide 1.5 mg/L
• In samples stored for some period
• CO 0
• Cyanide 0.2 mg/L

8
Anaerobic metabolism

• Reduction of nitrobenzodiazepines
• flunitrazepam, clonazepam, nimetazepam and
  nitrazepam
• Occurs within hours of death
• Almost all parent drug converted to 7-amino
  metabolites
• Flunitrazepam quickest
• Clonazepam slowest
• Metabolite should be target in post-mortem
  toxicology
• In clinical specimens parent drug dominant, plus
  some metabolite

Flunitrazepam
9
Changes in Nitrobenzodiazepines in Postmortem
Blood

• ?7Amino Flunitrazepam
• Flunitrazepam
• 7Amino Clonazepam
• Clonazepam

Robertson Drummer, 1995 J Forensic Sci, vol 40,
382-6
10
Effect of Postmortem Blood on Stability of
Clonazepam
11
Effect of Bacteria on Degradation of Nitrazepam,
Clonazepam, Flunitrazepam
Robertson Drummer, 1995 J Forensic Sci, vol 40,
382-6
12
Morphine SpeciesAdmission vs Autopsy
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Other forms of metabolism

• Hydrolytic Reactions
• heroin to morphine
• through 6-acetylmorphine
• occurs within minutes through esterases, both in
  life and after death
• Loss of heroin, 6-AM also occurs on storage of
  specimen
• acetylsalicylic acid (aspirin) to salicylic acid
• Any esterified drug including most pro-drugs
• eg cocaine

14
Other forms of metabolism

• Deconjugation of glucuronides and sulfates
• Also mediated by enzymes
• liver and
• bacteria in decomposing cases
• Examples
• Morphine glucuronides
• Salbutamol sulfate and glucuronide

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Stability of glucuronides

• Carroll et al AJFMP 21 pp323-7
• Morphine glucuronides unstable in postmortem
  blood, particularly
• ambient temperature
• bacteria present
• in decomposing specimens
• All glucuronides lost within days
• Gerostamoulos, 1999
• 15-20 lost over 28 days at 37 C
• Sawyer Forney, 1988 FSI 38pp 259-73
• Glucuronides degraded if blood contaminated with
  liver fluid

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Stability of morphine glucuronides
80
Conjugates degrade in postmortem blood,
particularly at RT
After Skopp et al 2001 JAT 25 pp2-7
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Case Example 1

• 29 year old woman found deceased in her home some
  6 days after last being seen
• substantially decomposed
• Postmortem found no significant natural disease
• Morphine 1.1 mg/L, total 1.2 mg/L
• Small amount of alcohol from putrefaction
• GP was charged with her murder
• alleged she was going to report him to medical
  board
• Basis of no morphine conjugates meant he gave a
  overdose IM/IV with intent to kill
• Quite likely that most of the conjugates
  converted back to morphine, hence elevating
  morphine substantially

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Other forms of metabolism

• Oxidation of sulfur-containing drugs to sulfoxide
  and sulfone
• Also mediated by bacteria and can occur quickly
• Most important in decomposing cases
• Examples
• Dothiepin
• Thioridazine
• Sulforidazine and mesoridazine

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Redistribution

• Diffusion of drug from high concentration to a
  lower concentration
• muscle to blood vessel
• Fat to blood vessel

10 mg/L
1000 mg/L

10 mg/L
Zero Time
20
Redistribution

• Diffusion of drug from high concentration to a
  lower concentration
• muscle to blood vessel
• Fat to blood vessel

10 mg/L
500 mg/L

20 mg/L
Hours later
21
Postmortem Increases on Blood Concentration
hydrophilic
lipophilic
Table shows average increases
22
Admission vs Autopsy Specimens
21 Heroin deaths
23
Beta-2 Adrenoceptor Agonists

• Comparison of blood concentrations at admission
  and at autopsy (n19)
• Admission 34.9 (1.5 - 136 ) ng/mL
• Autopsy 34.4 (2.7 - 154) ng/mL
• Conclusion No apparent PM redistribution

24
Beta-2 Adrenoceptor Agonists

• Effect of Site of Blood Sampling on Salbutamol
  Concentration (n9)
• Femoral Cubital Heart
• 100 137 66 254 260
• (89-273) (93-894)
• Conclusion Possible redistribution

25
Chemical Stability
Thioridazine and Amitriptyline at 21 C

• Thioridazine PBS 25 of original at 15 weeks
• liver 0 of original at 6 weeks
• PM blood 70 of original at 7 weeks
• Amitriptyline PBS 65 of original at 15 weeks
• liver 45 of original at 11 weeks
• PM blood 85 of original at 7 weeks

26
Stability of Drugs in Postmortem Tissues at
Ambient temperatures
0
PBS phosphate buffered saline, 15 weeks liver -
6 weeks postmortem blood - 7 weeks
27
Redistribution

• Diffusion of drugs from high to lower
  concentrations
• Highest in centrally collected blood
• Lowest in peripheral blood
• But still likely to elevate concentrations
• Often at least by factor of two
• Fat soluble drugs show biggest increase
• On-set occurs within hours of death

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Further Examples

• High degree of Redistribution
• Digoxin
• Propoxyphene
• Tri-cyclic antidepressants
• Lipid soluble opioids
• Methadone
• Fentanyl
• Most anti-psychotic drugs
• Haloperidol, thioridazine, clozapine etc
• Tetrahydrocannabinol
• Lipid soluble designer amphetamines

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Further examples

• Low degree of re-distribution
• Morphine and other water soluble opioids
• Paracetamol (acetaminophen)
• Amphetamine
• Cocaine and benzoyl ecgonine
• Low lipid solubility benzodiazepines
• Oxazepam
• Salbutamol (?) and beta-simulants

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How to minimize redistribution

• Take peripheral blood
• Especially femoral blood
• Vein tied off before blood is collected
• Even if femoral blood collected
• Redistribution will still occur!
• If in doubt
• Measure metabolite concentrations
• Measure liver concentration
• Take care for it not to be affected!

31
Morphine, M-3-G, M-6-G ratios
1. Morphine Morphine glucuronide
concentrations change with water content of blood
as well as morphine / conjugate
ratios 2. Implications in postmortem specimens
and estimation of time
Skopp et al, 1998 JAT 22 pp261-4
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Case Example 2

• 60-year old deceased man found in bed
• Has history of heart disease and is prescribed
  digoxin
• Toxicology
• Blood (heart) Digoxin 10 mmol/L
• Fatal Concentration !!
• Blood (femoral) Digoxin 5 mmol/L
• Toxic or fatal concentration !!
• Vitreous humour Digoxin 2 mmol/L
• Therapeutic concentration
• Death probably natural

33
Case Example 3

• Woman on pain medication, dies suddenly
• Toxicology
• Heart blood Oxycodone 9.2 mg/L
• Leg blood Oxycodone 0.9 mg/L
• Both concentrations potentially fatal, but heart
  blood elevated substantially
• Need to understand her dose regimen and if she
  may have taken additional tablets prior to death
• Take stomach contents recent overdose!

34
Case Example 4

• 40-year old woman found dead with no obvious
  cause of death after autopsy
• History of schizophrenia on clozapine (200 mg)
  and sertraline (75 mg)
• Toxicology
• Clozapine (leg) 1.5 mg/L
• Sertraline (leg) 1.1 mg/L
• Concentrations of drug high and potentially
  positive but redistribution likely even if
  peripheral blood taken!
• Death could be natural
• Sudden arrhythmic death in schizophrenics
• Need search of house re compliance and drug
  misuse
• Conduct liver and stomach analyses as well

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Conclusions

• PM redistribution is likely unless you know
  otherwise
• While peripheral blood minimizes this, some
  changes will still occur
• Clamping blood vessels to prevent central blood
  will assist
• For some drug stability and metabolism are
  important
• Use of liver and stomach contents analyses can
  assist in interpretation
• Full account of drug availability
• prescriptions and tablets at home are important
  together with other information pertinent to
  circumstances
• Know what pathologist has found at autopsy and
  histology

36
Reading material

• G. R. Jones and D. J. Pounder, Site dependence of
  drug concentrations in postmortem blood  a case
  study, J. Anal. Toxicol. 1987, 11, 186190
• M. D. Robertson and O. H. Drummer, Postmortem
  drug metabolism by bacteria, J. Forensic Sci.
  1995, 40, 382386
• Drummer OH. Forensic Pharmacology of Drugs of
  abuse. Arnolds (London) 2000
• Barnhart Fe et al. Post-mortem drug
  redistribution. Forensic Sci Reviews
  20012101-30.