Pharmcokinetics of ETHYL ALCOHOL IN FORENSIC VIEW

1. Pharmacokinetics of Ethyl Alcohol
Dr.Nafeeya
Department of Forensic Medicine & Toxicology

2. overview
Why we want to learn about ethyl
alcohol ?
Pharmacokinetics of ethyl alcohol
Mechanism of action of ethyl
alcohol
Medicolegal importance.

3. Important definitions
› Pharmacodynamics-Pharmacodynamics is the study of the biochemical and
physiological effects of drugs and their mechanisms of action .
› Pharmacokinetics-How the body acts on the drug.It involves absorption, distribution
,metabolism & drug excretion.
› Pharmacogenetics-Pharmacogenetics is the study of the genetic basis for variation in
drug response.
› Zero-order kinetics-implies that a constant amount of drug is eliminated from the blood
or the entire body per unit time.
› First-order kinetics-implies that a constant proportion is eliminated from the blood or
the entire body per unit time.

4. First order kinetics is a
concentration-dependent
process (i.e. the higher the
concentration, the faster the
clearance),
Zero-order kinetics is when a
constant amount of drug is
eliminated per unit time but
the rate is independent of the
concentration of the drug.

5. ETHYL ALCOHOL
• The most commonly abused drug in the world
• 75% of adults drink alcohol regularly
• In India, 11% of adults are classified as heavy drinkers
• Cost attributed to alcohol abuse exceed 200 billion dollars annually
• Traffic fatalities, homicides, rapes and suicides are all alcohol related
• Moderate alcohol use protect against cardiovascular diseases in individuals

6. Absorption
Simple passive
Diffusion
30 sec-blood,brain
5 minutes-stomach
20 minutes-kick start

7. First pass metabolism
Gastric & Liver ADH
First pass metabolism-lower blood alcohol
Absorption –elimination
Cemetidine
Rantac
Aspirin
Vd=0.5-0.7 L/kg

8. Factors affectingabsorption
• A Fatty meal
• Full Stomach
• Gender ,
• Body fat ,
• Drug interaction
• Alcohol Concentration
• Carbonated Drinks
• Habituation – before noon

9. Distribution
•Blood brain
barrier
•Insoluble in
fat
•Lungs- lost
by diffusion
•A=V-1 hr
•RBC-

10. METABOLISM

11. excretion
LIVER
KIDNEY
LUNG
SWEAT
ELIMINATION RATE =( BAC 1 – BAC 2)/ time difference
90%- oxidative
metabolism
10 % -
unchanged by
excretion via
lungs,kidney
,skin.

12. Factors modifying alcohol elimination rate
› Sex
› Age
› Race – B3 Class 1 ADH
› Food
› Biologic rhythms
› Alcoholism
› Drugs –Disulfiram

13. › AT ORGAN LEVEL
• Frontal lobes - most sensitive to
alcohol
• This results in mood changes
• Occipital lobe – visual disturbances
• Cerebellum – loss of coordination and
death from cardio-respiratory failure
› AT MOLECULAR LEVEL
› GABA RECEPTORS- sedative effects
› NMDA RECEPTORS –
› Glycine receptor
› Nicotinic Ach receptor
› G-protein –Coupled receptors
› 5HT3-receptor
› Voltage gated ca2+ channels
› Voltage activated K+ channels
MECHANISMOF ACTION
Compensatory
up regulation
of NMDAR
function

14. Causes of alcohol toxicity
Acetaldehyde formation
Mitochondrial damage
Oxidative stress
Hypoxia
Immune actions
Cytokine formation (TNF-alpha)
Kupffer cell activation

15. AUTOPSY FINDINGS
Hepatic necrosis Denk bodies

16. Cloudy swelling of parenchyma
CPM
Alcoholic CM
GD-PCT

17. Collection of specimens
•Blood
•Urine
•Saliva
•Breath
Laboratory test-chemical oxidation
Gas chromatography
Osmolol gap
Cavett ‘s test
Kozelka & hine test

18. Fresh –blood
Brain
CSF
Lung ,urine,
vitreous
Decomposed-Pleural fluid
Skeletal muscles
Embalmed
bodies-Sk-butt,
Blood ,urine
,vitreous,
viscera

19. Medicolegal importance
Alcohol &
traffic
accidents
Sudden
death
Manner of
poisoning
Alcohol
trauma &
delayed
death
Alcohol &
criminal
behaviour Ethanol

20. Sec 185 (a)
Sec 185 (b)
Sec 202
Sec 203
Sec 204
Alcohol is converted
generating a current
that is proportional to
the quantity of alcohol
present

21. Widmark’s formula
› 1.Amount of alcohol ingested by a suspect if his blood alcohol level is
known .
a=cpr
1. Alcohol ingestion in gram
2. Concentration of alcohol in the
blood
3. Weight of the body in kg
4. Widmark constant

22. Question?
› What is amount of alcohol ingested by a 70 kg male if his blood level to
30 mg%?
› Step 1-blood level must be converted from mg% to decigrams% by
dividing by 100.
› Step 2-application of formula
30mg % -0.3 decigram %
a=0.3x70x0.68
14.28 g
Male-0.68
Female-
0.55

23. › Step 3-conversion into c.c-divided by SG
› Step 4 – conversion into amount of liquor
Beer-8-12%
Wine-10-20%
Whisky ,gin,brandy-
40-60%
Rum,liquor-50-60%
14.28/0.79=18 cc of 100%
alcohol
Specific
gravity-
0.79
18x100/45=40 cc

24. Reference
› Goodnman& gilmans phamacologicalbasisof therapeutics13 thedition
› K.DTripathi–Essentialof pharmacology-6th edition
› Anil Aggrawal textbookof forensicmedicineandtoxicology
› Narayanareddy textbookof forensicmedicineandtoxicology
› Principlesof ForensicMedicine&ToxicologyRajeshBardalae
› KnightsForensicPathology-3rd edition
› V.VPillayForensicmedicinebook-4th edition