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Alcohol Physiology and Pharmacology

Alcohol Physiology and Pharmacology. Presented by the Vermont Forensic Laboratory Alcohol Program. DISCLAIMER. This presentation includes information that is intended to give you a basic understanding of alcohol physiology and pharmacology.

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Alcohol Physiology and Pharmacology

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  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. • http://www.cdc.gov/nchs/data/hus/hus06.pdf#068 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: 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. 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 allindividuals 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 0.100. • 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 0.080 level. 2013

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