Chapter 9 Physiology of Alcohol and Poisons

Chapter 9—Physiology of Alcohol and Poisons

Introduction—Objectives

1. Describe the role of a forensic toxicologist.

2. Discuss the legal importance of blood alcohol levels.

3. Explain the effects of alcohol and specific drugs and poisons on the body.

4. Discuss chemical agents that may be used for bioterrorism.

5. Describe analytical techniques for detection and identification of alcohol, poisons, and toxins in bodily fluids.

Introduction—Vocabulary

depressant—a chemical that slows the heart rate and brain activity and causes drowsiness

Immunoassay—a test that relies on the antigen-antibody response

Nystagmus—involuntary jerking movement of the eyes

Poison—a chemical that can harm the body if ingested, absorbed, or breathed in sufficiently high concentrations

Tolerance—in response to prolonged, heavy intake of alcohol or other drugs, the body’s need for progressively larger amounts of a chemical to cause the same levels of intoxication

Toxin—a type of poison produced naturally by living things

Michael Jackson

June 25, 2009, an accidental homicide

Homicide—a person died at the hands of another person

An overdose of medicines prescribed by Jackson’s doctor, Conrad Murray

Coroner’s determination—the interaction of anesthetics and sedatives caused Jackson to stop breathing.

History (Obj 9.1)

Early 1700’s—first use of chemistry to detect poisons

Early 19th century—toxicology became a new scientific discipline

France in 1840—Charles Lafarge trial involved testing for arsenic

Forensic toxicologists—study the legal and medical aspects of alcohol, drugs, poisons, and toxins in bodily fluids.

Alcohol (Obj 9.2, 9.3)

In everyday speech, alcohol usually refers to the ethanol used in alcoholic beverages.

In chemistry, alcohols are a group of substances with a hydroxyl group.

All alcohols are toxic in sufficient quantities

As little as 30 mL of methanol can kill

Ethanol, ethyl alcohol, is a colorless liquid obtained from fermented grains or fruits

Initial reaction to alcohol is euphoria

Alcohol is actually a depressant

Alcohol in the Body

Alcohol diffuses through the stomach and small intestines

As alcohol concentration increases:

• ability to respond to stimuli decreases

• temporary euphoria results from depressing inhibitions

• lose coordination and become confused

• memory diminishes

The liver metabolizes alcohol with an enzyme called alcohol dehydrogenase (ADH)

Resulting product is acetaldehyde

More enzymes break this into CO2 and H2O

The body can metabolize 15 to 30 mL of alcohol per hour

Excess alcohol is distributed to body tissues

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Stages of Intoxication

A blood alcohol concentration of 0.08 means 8 g of alcohol per 10,000 mL of blood

Alcohol affects different people differently

Concentration / Behavior
0.01 to 0.05 / Normal behavior
0.03 to 0.12 / Euphoria begins
0.09 to 0.25 / Vision blurs, loss of balance, sleepiness
0.18 to 0.30 / Speech slurs, dizzy, disoriented, emotional
0.25 to 0.40 / Standing and walking is difficult
0.35 to 0.50 / Impaired respiratory and circulatory systems
Over 0.45 / Potentially fatal

Stages of Intoxication

Factors affecting alcohol absorption

• Body weight

• How much alcohol is consumed

• Over what time period

• Amount of food in the stomach

• Frequency of drinking alcohol

• Body fat percentage

• Medications and popular energy drinks

Tolerance

Metabolic tolerance—the body produces larger amounts of alcohol dehydrogenase

Functional tolerance—a person displays fewer visible symptoms of intoxication without affecting blood alcohol concentration

Field Sobriety Tests

Horizontal gaze nystagmus (HGN) test

• Nystagmus is the involuntary jerking of human eyes, which increases with intoxication

Divided-attention tests

Breath tests

• Direct correlation between alcohol in the breath and alcohol in the blood stream

• Ratio is 1:2100

Blood and Urine Tests

Toxicology labs use gas chromatography/ mass spectrometry (GC/MS)

Gas chromatography separates the sample into individual components

Poisons (Obj 9.3, 9.4)

Eaten (ingested)

• 90% - at home, involving children

• household cleaners

Inhaled

• carbon monoxide

• sarin, a nerve gas

Injected

• heroin

Absorbed

• Poison sumac, mustard gas, ricin, anthrax

Drugs

Toxicological Testing (Obj 9.5)

Detect trace amounts of drugs in the blood, urine, and body tissues with

• thin layer chromatography,

• gas chromatography, and

• immunoassay techniques

Confirmation is achieved
using GC/MS.

Toxicological Testing

Reinsch test—for heavy metal poisoning

• Certain metals dipped in hydrochloric acid produce a silver-colored coating on copper

Emission spectroscopy or atomic absorption spectrophotometry—identifies the specific metal

Blood gas screenings—detects level of CO in the blood stream

Toxicological Testing

Immunoassay—measures the level of antibodies produced in response to antigens (poisons) entering the bloodstream

EMIT—enzyme-multiplied immunoassay technique

• Rapidly detects several drugs and their metabolites

Chapter Summary

Poisons are chemicals that harm the body if ingested, inhaled, or absorbed through the skin.

Forensic toxicologists investigate the legal and medical aspects of alcohol, drugs, poisons, and toxins in the body; also

• testifying as expert witnesses,

• collaborating with the medical examiner, and

• analyzing evidence.

The role of forensic toxicologist also includes:

• testing employees for drug use,

• screening athletes for drug use, and

• testing sexual assault victims for the presence of date rape drugs.

In everyday speech, alcohol usually refers to the ethanol used in alcoholic beverages.

In chemistry, alcohols are a group of substances with a hydroxyl group.

Alcohol is a depressant.

• Initially, it causes feelings of euphoria.

• When more is consumed,

• motor skills become impaired,

• brain function is depressed, and

• the person may even lapse into a coma and die.

The liver can metabolize about 15 to 30 mL of alcohol per hour. A person becomes intoxicated when consumption exceeds that.

When a driver is suspected of intoxication, several field sobriety tests are given

Presumptive tests

• horizontal gaze nystagmus and

• divided-attention tests

Conclusive test

• breath tests can determine blood alcohol levels.

How the poison enters the body determines its effect on the body

• inhaled poisons can cause asphyxia

• ingested poisons often target specific organs

Testing procedures

• Chromatography techniques, mass spectrometry, and immunoassay are used to detect various poisons and drugs in urine and blood

• Reinsch test detects heavy-metal poisoning

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