Toxicology Flashcards
What is the study of the harmful effects of chemical, biological, and physical agents on living organisms called?
Toxicology
Toxicology examines how these agents adversely affect health and living systems.
What is the role of forensics?
The use of science within the legal system
Forensics applies scientific principles to legal investigations.
What does postmortem toxicology involve?
Analyzing a dead body for toxins
The body’s reaction to chemicals can differ after death.
What are poisons?
Anything that harms a living organism
The dose of a substance determines its potential to be a poison.
What are the most frequent occurrences of poisoning?
Most cases result from:
* Social and economic stress or mental disorders
* Illicit substance abuse (minority)
* Substances administered against will
* Unintentional accidents
What is a key responsibility of a toxicologist?
Conduct toxicological analysis
Toxicologists analyze samples to identify poisons and drugs.
What is the National Poisons Information Service (NPIS)?
Advises NHS healthcare professionals on the diagnosis, treatment, and care of poisoned patients.
What is the role of a pathologist in toxicology?
Perform medico-legal autopsies to establish the cause of death
They attend suspicious deaths and estimate time of death.
What are common drugs of abuse?
Legal:
* Alcohol
* Medicines
Illegal:
* Heroin
* Cannabis
What does the Misuse of Drugs Act (1971) state?
It is offensive to:
* Possess a controlled substance unlawfully
* Possess a controlled substance with intent to supply
* Supply or offer to supply a controlled drug
* Allow premises to be used for drug use
What are the categories in the spectrum of drug use?
- Opiates (Morphine, heroin)
- Depressants (alcohol, barbiturates)
- Minor tranquilizers (benzodiazepines)
- Stimulants (cocaine)
- Hallucinogens (LSD)
- Others (cannabis)
What is the goal of toxicological screening techniques?
To confirm and quantify chemical presence
The choice of technique depends on analytical sensitivity and specificity.
What are the steps to toxicological analysis?
- Separation of poison and metabolites from biological material
- Identification
- Confirmation of identity
- Quantification
- Interpretation
What is acute exposure?
Contact with a substance that occurs once or for only a short time (up to 14 days)
It typically leads to immediate effects.
What is chronic exposure?
Contact with a substance that occurs for a year or longer
What are general symptoms of poisoning?
- Neurological
- Respiratory
- Cardiovascular
- Ocular
- Mouth
- GIT
What are the routes of administration/exposure?
- Intravenous
- Dermal
- Inhalation
- Rectal
- Sublingual
- Intraethecal
- Oral
What is the definition of drug metabolism?
The enzyme-catalyzed conversion of a drug into a chemically distinct substance
What is half-life (t1/2) in drug elimination?
Time taken for drug concentration to decline by half
What is the significance of dose-response curves?
They plot % response against log of dosage to determine lethal doses and compare toxicity of substances
What is postmortem redistribution (PMR)?
Artificially elevated drug concentration in heart after death
Drug levels change due to time between death and blood collection.
What factors affect the passage of drugs through cell membranes?
- Water solubility
- Lipid solubility
- Degree of ionization
- Molecular weight
- Active transport
What is the role of analytical methods in toxicology?
To confirm and quantify the presence of chemicals in biological samples
What are some examples of analytical techniques used in toxicology?
- Immunoassays
- Spot colour tests
- TLC
- GC
- HPLC
What is the main site for drug absorption in oral administration?
Gastrointestinal tract (GIT)
The GIT has a large surface area for absorption.
What is the significance of renal excretion?
It is the removal of intact drug from the body
What is oral administration?
Administration of drugs by mouth, easy for patient, high compliance
Drugs must cross through or between cell membranes to reach target, absorbed from GIT into the bloodstream
What is intravenous administration?
Direct administration of drugs into the bloodstream, bypassing first pass metabolism
This method allows for immediate drug effects
Define drug distribution.
The movement of a drug/chemical around the body, into and out of body tissues
What is the difference between excretion and elimination?
Excretion is the removal of intact drug from the body; elimination is the irreversible loss of drug by any mechanism
What is renal excretion?
The process of removing drugs from the body through the kidneys
What is biotransformation?
The process of chemical alteration of a drug in the body, primarily occurring in the liver
What is first pass metabolism?
The metabolism of a drug in the liver after being absorbed from the gastrointestinal tract but before reaching systemic circulation
What does enterohepatic circulation refer to?
The reabsorption of eliminated molecules from bile back into the bloodstream
List factors affecting drug passage through cell membranes.
- Water solubility
- Lipid solubility
- Degree of ionisation
- Molecular weight
- Active transport
Define drug metabolism.
The enzyme-catalysed conversion of a drug into a chemically distinct substance
What is half-life (t1/2)?
The time taken for drug concentration to decline by half
What is bioavailability?
The amount of drug absorbed relative to the dose administered
Describe a dose-response curve.
A plot of % response (e.g. % viability) against the logarithm of dosage, typically a sigmoid curve
What does LD50 represent?
The lethal dose that kills 50% of a population
What is postmortem redistribution (PMR)?
The phenomenon where drug concentrations, especially in the heart, increase after death as time passes until blood collection
What is the order of specimen collection after death?
Femoral > iliac > subclavian vessels > heart
What are common specimen types for toxicology?
- Blood
- Vitreous humor
- Liver
- Muscle
What is the role of the National Poisons Information Service (NPIS)?
To advise NHS healthcare professionals on the diagnosis, treatment, and care of poisoned patients
What are poisons?
Any substance that harms a living organism, where the dose determines its toxicity
What are the most frequent occurrences of poisoning?
- Social and economic stress
- Mental disorders
- Illicit substance abuse
- Unintentional accidents
What is the role of a toxicologist?
To identify drugs and poisons, screen throughout the body, and suggest possible effects on victims
List types of common drugs of abuse.
- Alcohol
- Medicines
- Heroin
- Cannabis
What is the Misuse of Drugs Act (1971)?
UK legislation that prohibits unlawful possession, supply, and use of controlled substances
What are the common pharmacological groups of drugs of abuse?
- CNS stimulants
- Narcotic analgesics
- Hallucinogens
- Hypnotics
What is acute exposure to toxicants?
Contact with a substance that occurs once or for a short time (up to 14 days)
What is chronic exposure to toxicants?
Contact with a substance that occurs for a year or longer
List general symptoms of poisoning.
- Neurological
- Respiratory
- Cardiovascular
- Ocular
- Mouth
- GIT
What are the steps involved in toxicological analysis?
- Separation of poisons and metabolites
- Identification
- Confirmation of identity
- Quantification
- Interpretation
What are presumptive tests?
Qualitative tests that quickly identify substances based on characteristic color changes
What does ADMET stand for?
- Absorption
- Distribution
- Metabolism
- Excretion
- Toxicity
What is the reward system in relation to drug use?
Involves dopamine pathways: mesocortical, mesolimbic, and nigro-striatal systems
What is the role of a pathologist in toxicology?
To perform medico-legal autopsies, estimate time of death, and remove specimens for analysis
