Alcohol Physiology and Pharmacology

Vermont Forensic Laboratory

DISCLAIMER This presentation includes information

that is intended to give the students a basic understanding of alcohol physiology and pharmacology.

It is not designed to make the students experts in this subject.

What is Alcohol?

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

Who Uses Alcohol?

Alcohol is the most widely used drug.In 2013, 86.8 percent of people ages 18

or older reported that they drank alcohol at some point in their lifetime; 70.7 percent reported that they drank in the past year; 56.4 percent reported that they drank in the past month.

http://pubs.niaaa.nih.gov/publications/AlcoholFacts&Stats/AlcoholFacts&Stats.htm

Alcohol-Related Deaths

Nearly 88,000 people die from alcohol-related causes annually, making it the third leading preventable cause of death in the United States.

In 2013, alcohol-impaired driving fatalities accounted for 10,076 deaths (30.8 percent of overall driving fatalities).

http://pubs.niaaa.nih.gov/publications/AlcoholFacts&Stats/AlcoholFacts&Stats.htm

Alcohol Physiology

AbsorptionDistributionMetabolismElimination

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.

What can affect absorption?

Stomach emptying (opening of pyloric sphincter)

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

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.

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

Distribution

Ethanol is hydrophilic = water loving.

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

Volume of Distribution (Vd)

BAC is affected by the volume of distribution.

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

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 of a man of the same size.

Same issue would occur between a lean person and an obese person of the same weight.

Blood Alcohol Concentration

The amount of ethanol found in a sampled portion of blood.

Typically expressed as a percentage or in terms of g/100ml.

AKA: BAC

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)

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

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.

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)

Elimination

The rate of elimination is constant and not dose dependent.

Elimination

Typical elimination: 0.018-0.022%/hour

Range: 0.010-0.030%/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 a majority of the population.

What can affect Elimination?

Gender: Women tend to eliminate faster Experience: Experienced drinkers eliminate

faster.

Person to person variability exists as well as inter-day variability for the same person.

Some medications and fructose may affect elimination to a minor degree by increasing or decreasing the rate.

What does NOT affect elimination?

Coffee Cold showers Exercise Sleep

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.

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

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.

The Effects of Alcohol

3

2

1

Low Level Impairment

Feeling of well-being Relaxation Decreased inhibitions Euphoria Lowering of caution Some minor impairment of

reasoning and memory

Mid Level Impairment

Impairment of balance, speech, vision, reaction time, and hearing.

The ability to multi-task is reduced.Judgment and self-control are reduced. Caution, reason and memory are

impaired.

High Level Impairment

Gross motor impairment and lack of physical control.

Blurred vision and major loss of balance.Judgment and perception are severely

impaired.Exaggeration of emotions.

Extremely High Level Impairment

Feeling dazed/confused or otherwise disoriented.

Limited perception of pain. Blackouts are likely at this level.All mental, physical and sensory

functions are severely impaired. Possible onset of coma or death due to

respiratory arrest.

Impairment

Cognitive skills are affected first and at lower concentrations.

Overlap of effects occur between levels. Observable signs may be altered by tolerance.

Impairment

Speed at reaching BAC may effect observable signs of impairment.

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

Tolerance

Behavioral: An individual accustomed to a certain BAC may learn to hide outward signs of intoxication. Walking and talking may seem normal.

Tolerance

Physiological: The body is accustomed to the alcohol and has “learned” how to eliminate it quickly.

May have increased levels of ADH or higher usage of secondary pathway.

Tolerance

Impairment still exists to the same degree in terms of cognitive abilities.

Ability to multi-task and react quickly to a changing situation is still impaired.

This is well researched and documented.

Tolerance

Tolerant ≠ Sober

Heavy Drinkers

Some heavy drinkers may rarely reach a zero BAC.

Predicting BAC

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.

The Standard Drink

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

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.

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.

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.

Retrograde Extrapolation

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

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 0.080.3) A drink has been consumed after or

within 30 minutes of operation.

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.