Forensic Toxicology. Chapter 17. Mrs. Svedstrup

Transcription

1 Forensic Toxicology Chapter 17 Mrs. Svedstrup

2 Forensic Toxicology Toxicology is study of harmful effects of drugs and poisons on living things Forensic toxicology is legal application of toxicology to criminal and civil cases Toxicology is part of science of pharmacology, which is the study of drugs and their harmful or beneficial effects on living things

3 Principles of Pharmacology Pharmacologists study all sorts of drugs and poisons Learn what happens when a drug is taken and what effects it has on an organism What happens when a drug is taken is known as pharmacodynamics

4 Drug Intake Drugs can be administered by Swallowing a powder or pill Dissolving powder in liquid and drinking it Intramuscular, subcutaneous or intravenous injection Best method for injection for drug depends on how it interacts with a particular organ Some drugs are protected (enteric dosage forms)

5 Absorption Once drug enters body, it enters blood stream If inhaled, enters through alveoli of lungs With exception of oral ingestion, drug user has not control over rate of absorption of drug

6 Circulation of Drugs in Bloodstream Drugs generally have most important effects in brain Advancement of pharmaceutical industry allows for drugs to almost particularly interact with the brain resulting in predictable effect Higher concentration of drugs allows for more pronounced effects

7 Circulation of Drugs Certain effects may not appear at low drug concentrations Some drugs have a tendency to build up and collect in fatty tissues, which can make them dangerous over time Mercury, lead, pesticides; LSD, marijuana are all examples of drugs that may collect in body

8 Elimination of Drugs from Body After reaching a maximum, concentration of drug in body will begin to decrease, which is referred to as half-life of drug Half-lives of drugs vary greatly Decrease in half-life of drugs is affected by metabolism and elimination

9 Metabolism As drugs circulate through body, sooner or later they reach liver Liver has ability to change drug into metabolite Primary metabolite may be metabolized into secondary metabolite Liver metabolism accomplished two things: Changes drug into less toxic substance Changes drug into form that is easier to eliminate in urine

10 Metabolism Me Me N N R H H R H H R R S S R S R S AcO O H OAc HO O H OH Heroin Morphine

11 Elimination Drugs may be eliminated in several ways: Exhaled in breath in volatile drugs Sweated out in water soluble drugs Through urine as drug itself Through metabolism in liver Person has no control over rate at which this happens Process is entirely under control of liver and kidneys

12 Synergism Known as the magnified effects from a combination of drugs Sum of two effects of drugs as a whole is greater than two parts of individual drugs

13 Tolerance Occurs when increasing doses of a drug are required to keep the same level of effects on the person Reverse tolerance occurs when users get more heightened effects over time from use of the drugs

14 Addiction vs. Dependence Drug addiction is a physical process Person develops biochemical changes to tolerate drugs Body requires drug on a regular basis Failure to provide drug causes withdrawal Drug dependence is a psychological, not physical, dependence on drugs

15 Ethyl Alcohol Ethanol is active ingredient in all liquor, wine and beer Concentration is measured in proof (100 proof = 50% alcohol) Ethanol is a central nervous system depressant Acts as a mild tranquilizer and kills nerve cells One ounce of alcohol kills 10,000 nerve cells

16 Ethyl Alcohol H 3 C CH 2 OH

17 Blood Alcohol Concentration (BAC) Government regulates amount of alcohol a person may drink before driving vehicle BAC is measured in weight/volume percent Number of grams of alcohol present in 1 deciliter(100 ml) of blood Level of BAC reflects impairment people experience as a result of alcohol

18 Absorption of Alcohol Ultimate concentration and effects that alcohol will have depend upon the rate at which it is absorbed Depends on concentration of alcohol in drink and contents of stomach at time of drinking More concentrated drink, faster alcohol reaches bloodstream Food slows absorption of alcohol in stomach due to competing with it

19 Circulation of Ethanol in the Bloodstream Once absorbed through stomach and small intestine, alcohol circulates throughout body First acts on outer surfaces of brain (affects motor coordination) If alcohol penetrates deeply into brain, will affect autonomic nervous system, which has involuntary functions such as breathing Degree of effect on brain depends on BAC

20 Elimination of Ethanol Liver metabolizes alcohol by changing it to acetaldehyde and then acetic acid Both are oxidation reactions and occur as a result of liver enzymes As ethanol is metabolized, metabolites are dissolved in urine Ethanol metabolism occurs at rate of.015% per hour May be eliminated through breath and perspiration

21 Alcohol Metabolism O H 3 C CH 2 OH H 3 C CH O HO C CH 3 Ethyl alcohol Acetaldehyde Acetic acid

22 Maximum Blood Alcohol Concentration As ethanol is absorbed into blood stream, BAC rises Body starts metabolizing and eliminating ethanol 95% of ethanol is eliminated by metabolism and subsequent elimination Widmark (1930s) addresses alcohol absorption Carbohydrates impede alcohol most efficiently of foods

23 Widmark Curve BAC.1.05 b c d e a Empty stomach Full stomach Time in hours

24 Amount of Alcohol to Get Drunk Male- volume= wgt X BAC /3.78 Female- volume = wgt X BAC/4.67

25 Drunk Driving Laws Implied consent- signature of license implies you are giving permission to submit to a blood or breath alcohol test if you are found intoxicated Refusal may result in loss of license Length of license loss is generally days Depending on state, wording may be impaired or intoxicated

26 Testing Alcohol Levels Breathalyzers work by a type of chemical reaction called oxidation/reduction or redox Electrons are moved from one substance to another Newer fuel cell technology allows for alcohol present to produce electricity. The more alcohol present, the more electricity produced

27 Field Sobriety Testing Examples of tests include: Walk and turn Stand on one foot Horizontal gaze nystagmus Results of test are admissible in in court as evidence of impairment

28 Measurement of BAC Drunk driving cases represent more than ½ of the case load of forensic toxicologists nationwide Depending on jurisdiction blood or breath test may be required Most popular method of BAC analysis is by gas chromatography using headspace analysis