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Alcohol Physiology and Pharmacology

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Presentation on theme: "Alcohol Physiology and Pharmacology"— Presentation transcript:

1 Alcohol Physiology and Pharmacology
Presented by the Vermont Forensic Laboratory Alcohol Program

2 DISCLAIMER This presentation includes information that is intended to give you a basic understanding of alcohol physiology and pharmacology. It is not designed to make you an expert in this subject. 2013

3 What is Alcohol? Any Carbon attached to an OH group.
Ethanol, Methanol, Isopropanol etc. It is a drug. It is a poison. It is a Central Nervous System (CNS) Depressant. 2013

4 Beverage Alcohol Beer, Wine, Liquor, Cordials, all contain ethanol.
Amount of ethanol equates to the strength of the drink. Percentage of alcohol is 50% of “Proof”. 2013

5 Production Alcoholic beverages up to approximately 15% ethanol are produced via fermentation. At that level the ethanol kills the yeast so production ceases. Liquors are produced via distillation. Fortified beverages are initially fermented and then distilled ethanol is added. 2013

6 Who Uses Alcohol? Alcohol is the most widely used drug.
Only ~25% of the population will abstain from alcohol use through their lifetime. 2013

7 Absorption Drink is consumed orally (typically)
10-20% of the alcohol is absorbed directly through the stomach wall. 80-90% is absorbed through the wall of the small intestine. Alcohol is a small molecule and does not require digestion to be absorbed. 2013

8 What can affect absorption?
Stomach emptying (opening of pyloric sphincter) Food Type of beverage Proof of liquor Gastric bypass Speed of consumption 2013

9 What can affect absorption?
In terms of a DUI, we are concerned with alcohol consumed within 30 minutes of operation. Some or all may still remain in the stomach. 2013

10 Distribution Once the alcohol is absorbed it circulates in the blood throughout the body. Observable effects are a reaction to the alcohol in the brain. 2013

11 Distribution Ethanol is hydrophilic = water loving.
Ethanol moves into muscles & organs but not into adipose tissue or bone. 2013

12 Volume of Distribution (Vd)
BAC is affected by the volume of distribution. Vd changes based on size, gender and body mass index. 2013

13 Volume of Distribution (Vd)
Women tend to have higher levels of adipose tissue which means that the Vd is smaller resulting in a higher BAC than would be expected for a man of the same size. Same issue would occur between a lean person and an obese person of the same weight. 2013

14 Metabolism Once consumed some alcohol is metabolized in the stomach by an enzyme, ADH. ADH = Alcohol Dehydrogenase, the prime enzyme responsible for metabolism. Main site of metabolism is in the liver. Intestine Portal Vein Liver 2013

15 Elimination Elimination: Includes excretion and the metabolic breakdown of ethanol. 97-98% of alcohol eliminated is through the breakdown into its metabolites via ADH. The effective dose of alcohol overwhelms the body’s ability to metabolize it away. (Until levels reach below 0.01) 2013

16 Elimination Excretion: 2-3% of the alcohol consumed is excreted via sweat, breath and urine. Excretion allows us to measure alcohol in a breath sample. 2013

17 Elimination The rate of elimination is constant and not dose dependent. 2013

18 Elimination Typical elimination: 0.018-0.022%/hour
Range: %/hour Extreme cases: %/hour (estimates) 0.015%/hour used in calculations as it meets or underestimates the “true” elimination rate of most of the population. 2013

19 What can affect Elimination?
Gender: Women tend to eliminate faster Experience: Experienced drinkers eliminate faster. Variability: From person to person Over the course of the day Some medications and fructose Minor but can increase or decrease the rate. 2013

20 What does NOT affect elimination?
Coffee Cold showers Exercise Sleep 2013

21 Blood Alcohol Concentration
The amount of ethanol found in a sampled portion of blood. Typically expressed as a percentage or in terms of mg/dl. AKA: BAC 2013

22 Breath Alcohol Concentration
“Breath Alcohol Concentration” used when concerning a breath test. (BrAC) Breath values reported as grams of alcohol per 210 liters of expired air. (g/210L) 2013

23 What is Impairment? Impairment = Deterioration of one’s physical or mental abilities from normal. May be caused by many things. Alcohol impairment = the deterioration is due to alcohol consumption. 2013

24 Impairment Measurable impairment in laboratory settings as low as 0.02. Abilities used to operate a vehicle are affected at 0.05. The ability to drive in all individuals is affected at 0.08 level. 0.08 Per se limit is to reflect this fact. 2013 NHTSA 2001

25 Impairment Legal limit has decreased as scientific understanding has increased. Scientific Communities have urged a reduction to 0.05. Some countries as low as 0.02. 2013

26 Impairment Speed at reaching BAC may affect observable signs of impairment. Mellanby Effect: Impairment is greater when BAC is rising as opposed to falling. 2013

27 Predicting BAC 2013

28 Predicting BAC Widmark Equation: Used by chemists to determine the impact of a drink to a person’s BAC. Based on type of beverage, weight and gender of individual. 2013

29 The Standard Drink A standard drink is the equivalent dose of beer, wine and liquor which yield the same BAC. 2013

30 The Myth of the Standard Drink
Why is it a myth? Drinks are not always poured to the same amount. Alcohol concentrations of beer and wine vary. Home mixed drinks are substantially stronger than those served at an establishment. 2013

31 The Myth of the Standard Drink
A “standard” drink will be used by the chemist when no other information is given about what was actually consumed. Keep in mind that a beer is not a beer. There can be great variations. 2013

32 Retrograde Extrapolation
AKA Relation Back A calculation used by chemists to determine what an alcohol concentration would have been at an earlier point in time. Based on test result, time of test, time of operation and any drinking history available. 2013

33 Retrograde Extrapolation
The Widmark equation is used when drinking occurs after or within 30 minutes of operation. 2013

34 Retrograde Extrapolation
A relation back calculation is required: The test occurs more than 2 hours from the time of operation. The test result is below a A drink has been consumed after or within 30 minutes of operation. 2013

35 Things to Remember! Alcohol is a CNS Depressant.
Alcohol is eliminated at a constant rate per hour. Absorption and elimination occur simultaneously. Impairment begins at very low BAC. Everyone is impaired to operate a motor vehicle at an level. 2013


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