Alcohol Physiology and Pharmacology

Presented by the Vermont Forensic Laboratory Alcohol

Program

2013

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.

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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.

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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”.

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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.

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Who Uses Alcohol?

Alcohol is the most widely used drug.

Only ~25% of the population will abstain from alcohol use through their lifetime.

http://www.cdc.gov/nchs/data/hus/hus06.pdf#068

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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.

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What can affect absorption?

Stomach emptying (opening of pyloric sphincter)

Food Type of beverage Proof of liquor Gastric bypass Speed of consumption

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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.

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Once the alcohol is absorbed it circulates in the blood throughout the body.

Observable effects are a reaction to the alcohol in the brain.

Distribution

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Distribution

Ethanol is hydrophilic = water loving.

Ethanol moves into muscles & organs but not into adipose tissue or bone.

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Volume of Distribution (Vd)

BAC is affected by the volume of distribution.

Vd changes based on size, gender and body mass index.

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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.

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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

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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)

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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.

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Elimination

The rate of elimination is constant and not dose dependent.

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Elimination

Typical elimination: 0.018-0.022%/hour

Range: 0.010-0.035%/hour

Extreme cases: 0.065-0.075%/hour (estimates)

0.015%/hour used in calculations as it meets or underestimates the “true” elimination rate of most of the population.

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What can affect Elimination?

Gender: Women tend to eliminate fasterExperience: Experienced drinkers

eliminate faster.Variability:

From person to personOver the course of the day

Some medications and fructoseMinor but can increase or decrease the rate.

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What does NOT affect elimination?

Coffee Cold showers Exercise Sleep

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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

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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)

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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.

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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.

NHTSA 2001

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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.

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Impairment

Speed at reaching BAC may affect observable signs of impairment.

Mellanby Effect: Impairment is greater when BAC is rising as opposed to falling.

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Predicting BAC

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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.

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The Standard Drink

A standard drink is the equivalent dose of beer, wine and liquor which yield the same BAC.

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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.

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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.

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Retrograde Extrapolation

AKA Relation BackA 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.

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Retrograde Extrapolation

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

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Retrograde Extrapolation

A relation back calculation is required:

1) The test occurs more than 2 hours from the time of operation.

2) The test result is below a 0.100.

3) A drink has been consumed after or within 30 minutes of operation.

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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 0.080 level.