Toxicology Flashcards
Study of poisons and xenobiotics
TOXICOLOGY
substances that can cause harmful effects upon exposure
Poisons
substances that are not normally found or produced by the body
Xenobiotics
4 MAJOR INTERRELATED DISCIPLINES OF TOXICOLOGY
Mechanistic Toxicology
Descriptive Toxicology
Forensic Toxicology
Clinical Toxicology
Dose-Response Mechanism
Mechanistic Toxicology
Dose of toxin that will result in harmful effects
Dose-Response Mechanism
Determines the dose of toxin that will result in harmful effects
Mechanistic Toxicology
Provides a basis for rational therapy design from the known harmful dose
Mechanistic Toxicology
Development of laboratory tests to assess the degree of exposure in individuals
Mechanistic Toxicology
involves risk assessment of toxins
Descriptive Toxicology
Performed by FDA and part of pre-clinical studies of novel drugs
Risk assessment
Assesses toxic, lethal, and effective dose
Risk assessment (Descriptive Toxicology)
Uses result from animal experiments to predict what level of exposure will cause harm in humans
Descriptive Toxicology
Medical & legal consequence of toxin exposure; performed in autopsy
Forensic Toxicology
Establishes & validates analytical performance of tests methods used to generate evidence in legal situations
Forensic Toxicology
Study of interrelationship between toxin exposure and disease states (toxic effect)
Clinical Toxicology
Emphasis on diagnostic testing and therapeutic intervention (antidote to toxins)
Clinical Toxicology
ROUTES OF TOXIN EXPOSURE
Ingestion – most often in clinical setting
Inhalation
Transdermal absorption
how is toxin absorbed in GI tract
Passive diffusion
*not requiring transport protein
substances readily diffusible across cell membranes along GI
Hydrophobic (non-polar) subs.
substances that cannot passively diffuse across cell membranes (require transporters)
Ionized subs.
absorbed in the stomach; proteinated by gastric juices → became non-ionized → readily absorbed by stomach
Weak acids
absorbed in the intestine (neutral to slightly alkaline pH)
Weak bases
some toxins that are not absorbed by GI produce these local effects given that they are toxic to that site
diarrhea
malabsorption
GI bleeding
Factors that influence toxin absorption
Rate of Dissolution
GI mobility
Resistance to degradation
Interaction with other substances in GI
Effect in absorption rate when there is imbalance in mobility such as low bowel movement, diarrhea
Less/decreased toxin absorption
T/F
Some toxins are resistant to degradation = remains intact in GI (may or may not be absorbed by the GI)
T
Effect in absorption rate when toxins interact with other GI substances
Decreased rate of absorption
single, short-term exposure to toxic substance
Acute toxicity
repeated exposure for extended period of time
Chronic toxicity
dose that would predict to produce a toxic response in 50% of the population
TD50 (toxic dose)
dose that would predict death in 50% of the population
LD50 (lethal dose)
dose predicted to be effective or have a therapeutic benefit in 50% of the population; used in therapeutic drugs that may cause adverse effects
ED50 (effective dose)
Rapid, simple, qualitative procedure intended to detect the presence of specific substance
Screening test
test that has good sensitivity, lack specificity
Screening test
Quantitative tests; specific for a single substance or class
Confirmatory test
Example of Confirmatory tests for toxic agent analysis
TLC (Thin Layer Chromatography), GC (Gas Chromatography)
ICP-MS/AA (Inductively Coupled Plasma – Mass Spectrometry/Atomic Absorption)
GC-MS (Gas Chromatography-Mass Spectrometry)
test used for inorganic substance
ICP-MS/AA (Inductively Coupled Plasma – Mass Spectrometry/Atomic Absorption)
test used for organic substance
GC-MS (Gas Chromatography-Mass Spectrometry)
reference method for toxic agents analysis
GC-MS (Gas Chromatography-Mass Spectrometry)
Common CNS depressant
Alcohol
effect of LOW dose exposure to alcohol
Confusion
Euphoria
Disorientation
effect of HIGH dose exposure to alcohol
Unconsciousness
Paralysis
Death
Sample used for alcohol det.
Whole Blood
Serum
Plasma
Methods used for alcohol det.
Enzymatic method
Gas Chromatography
Osmometry methods (Osmolal Gap)
test that uses alcohol dehydrogenase (ADH)
Enzymatic method
Reference method for ethanol det.; may quantitate methanol and isopropanol
Gas Chromatography
Computed method; NOT ethanol specific (may increase in other conditions)
Osmometry methods (Osmolal Gap)
formula of Osmometry methods (Osmolal Gap)
Osmolal Gap = MEASURED osmolality - CALCULATED osmolality
serum ethanol if there is ↑ 10 mOsm/Kg
60 mg/dL serum ethanol
Most common toxicant & substance of abuse (US)
Ethanol (Grain Alcohol)
aka ethanol
Grain Alcohol
Depresses CNS; ↑ heart rate and BP
Ethanol (Grain Alcohol)
a Vasopressin inhibitor (↑ urine output leading to diuresis)
Ethanol (Grain Alcohol)
Effects of ethanol intoxication
blurred vision
incoordination
slurred speech and coma
“hangover symptoms”
FATAL DOSE of ethanol
300-400 mL (pure alc.) in <1 hr
TOXIC BLOOD LVL of ethanol
> 400 mg/dL
> 500 mg/dL: requires hemodialysis to filter all alcohol
ANTIDOTE for ethanol intoxication
Diazepam
method for ethanol det.
Gas Chromatography
Enzymatic (ADH) method
T/F
Serum and plasma have lower ethanol conc. than whole blood
F
Serum and plasma have HIGHER ethanol conc. than whole blood (ethanol is uniformly distributed in body water such as serum or plasma)
conditions that causes false INCREASED ethanol
Use of alcohol antiseptic during venipuncture
Failure to use fluoride tubes
Tube necessary for blood collection during ethanol det.
Fluoride tubes (prevent glycolysis and bacterial fermentation as they produce alc. (byproduct)
aka methanol
Wood Alcohol
Most commonly used solvent
Methanol (Wood Alcohol)
Homemade liquor contaminant
Methanol (Wood Alcohol)
Methanol (Wood Alcohol) metabolites
formaldehyde
formic acid
Methanol (Wood Alcohol) metabolite that causes intoxication
Formic acid
T/F
Ethanol has more severe intoxication than methanol
F
METHANOL has more severe than ethanol
Effects of methanol intoxication
metabolic acidosis
pancreatic necrosis
ocular toxicity (frank blindness)
toxins that can cause ocular toxicity (frank blindness)
Methanol (Wood Alcohol)
FATAL DOSE of methanol
60-250 mL
TOXIC BLOOD LVL of methanol
> 50 mg/dL
ANTIDOTE for methanol intoxication
Sodium Bicarbonate
Commonly available alcohol
Isopropanol (Rubbing Alcohol)
aka Isopropanol
Rubbing Alcohol
Isopropanol (Rubbing Alcohol) metabolite
acetone
enzyme that converts isopropanol to its metabolite
hepatic ADH
has longer halflife in the body compared to ethanol metabolite
acetone
has similar to ethanol toxicity but has a longer intoxication due to its metabolite having a longer half life
Isopropanol (Rubbing Alcohol)
FATAL DOSE of Isopropanol
250 mL
ANTIDOTE for Isopropanol intoxication
Active charcoal
aka Ethylene Glycol
1,2-ethanediol
Component of hydraulic fluid and anti-freeze
Ethylene Glycol (1,2-ethanediol)
Accidentally ingested by children due to its sweet taste
Ethylene Glycol (1,2-ethanediol)
Ethylene Glycol (1,2-ethanediol) metabolites that can cause severe metabolic acidosis
oxalic acid
glycolic acid
Effects of Ethylene Glycol intoxication
severe metabolic acidosis
Ingestion (↑levels): Calcium oxalate crystals
deposition in renal tubules → kidney damage
Blood ethanol level if there is no obvious impairment
0.01-0.05%