Lecture 12: Forensic Toxicology Flashcards
What is forensic toxicology?
- Study how human/animals are affected by drugs and poisonous substances
- Other disciplines: Analytical/clinical chem, pharmacology
Relation to medical or legal investigation of death, poisoning, and drug use
Who is considered the Father of Forensic Toxicology?
Mathieu Orfila
He published “Traite de Poisons,” the first scientific work on the detection of poisons.
What are the main responsibilities of a forensic toxicologist?
- Detect and identify drugs and poisons in body fluids, tissues, and organs
- Identify a drug overdose or monitor drug intake
- Work in crime laboratories, medical examiners’ offices, and health facilities
- Measure the amount of alcohol or other abused drugs for legal violations
What are some categories of overdose?
- Analgesics
- Antidepressants
- Sedatives/hypnotics/antipsychotics
- Cardiovascular drugs
- Alcohols
What is the lethal dose of cyanide?
2.8 mg/kg
Cyanide is a well-known anion poison.
What are the six main classes of common poisons?
- Anions
- Corrosive poisons
- Gaseous and volatile poisons
- Metal and metalloid poisons
- Pesticides
- Toxins
Name two examples of corrosive poisons.
- Concentrated sulfuric acid (H2SO4)
- Sodium hydroxide (caustic soda, NaOH)
Upon contact, destroys body tissues, e.g. ingestion -> surface damage to mouth and intestinal tract
Name two examples of anions poisons.
- F- : key ingredient in bleach
- NO3: Blue Baby Syndrome
Name two examples of gaseous and volatile poisons
- Carbon monoxide (CO): Cherry-pink color
- Hydrogen cyanide (HCN): Deeper red color
Name examples of metal and metalloid poisons
- Lead (Pb)
- Arsenic (As)
- Mercury (Hg)
Symptoms: Vomiting and diarrhoea (confused with Cholera)
Persists in body after death
Name the quote that suggests “the dose makes the poison”
“All things are poison and nothing is without poison;
only the dose makes a thing not a poison” (Paracelsus)
What is LD50?
The dose of a toxin which will kill 50% of a group of test subjects (Lethal Dose of 50%)
The lower the LD50, the more toxic the substance.
How is the toxicity of a substance determined?
- Bioassay
- Factors like health status, age, and accumulation affects toxicity
What is biotransformation?
The conversion of drugs and other toxins into metabolites or breakdown products.
Which organ is primarily responsible for the metabolism of drugs?
Liver
Liver cells (hepatocytes) are actively metabolizing cells.
What is the secondary organ responsible for metabolism of drugs?
Kidney
Susceptible to toxins because of large blood flow (25%)
What is the role of forensic toxicology in Hong Kong?
- Investigation of cause and manner of death
- Analysis of opiate and non-opiate drugs in urine samples
- Analysis of blood or urine samples from suspected impaired drivers
What is Acetaminophen toxicity?
- Too much ingested causes formation of NAPQI metabolite
- Causes liver cell death
Name the five modes of intake of drugs/poisons
- Ingestion
- Inhalation
- Skin contact
- Mucous member contact
- Injection
What is the purpose of drug analysis?
- Identify the identity of the drug
- Quantify the amount of the drug
What are the two tiers of analysis for drugs and poisons?
- Initial test: Narrow range, indicate presence of analytes
- Confirmative test: For quantification
Confirmatory tests include GC-MS or LC-MS
What type of test is usually used for the initial drug screening?
Color form tests
These tests are quick and specific.
What is ELISA?
Enzyme-linked immunosorbent assay
It is a common immunoassay technique used for the analysis of body fluids.
True or False: The dose makes the poison.
True
This concept was famously articulated by Paracelsus.
Fill in the blank: The main index used in most toxicology studies is _____
LD50
What is the significance of NAPQI formation in alcoholics?
Alcoholics have enhanced P450 oxidase activity, increasing the amount of NAPQI formation.
What is the role of kidneys in metabolism?
They carry out metabolism of some drugs and may convert non-toxic substances to toxic metabolites.
What is the main goal of confirmatory testing in drug analysis?
To quantify the amount of the drug.
