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%
Blood ethanol level if there is mild euphoria, decrease inhibitions, some impairment of motor skills
0.03-0.12%
Blood ethanol level if there is decrease inhibitions, loss of critical judgment, memory impairment, diminished reaction time
0.09-0.25%
Blood ethanol level if there is decrease inhibitions
0.03-0.25%
Blood ethanol level if there is mental confusion, dizziness, strongly impaired motor skills (staggering, slurred speech)
0.18-0.30%
Blood ethanol level if there is inability to stand or walk, vomiting, impaired consciousness
0.27-0.40%
Blood ethanol level indicating coma and possible death
0.36-0.50%
Produced by incomplete combustion of carbon-containing substances
Carbon monoxide (CO)
Colorless, odorless and tasteless gas that is rapidly absorbed into the blood
Carbon monoxide (CO)
Carbon monoxide (CO) has _____X more affinity to Hb than O2
200–225x
caustic agents of carbon monoxide (CO)
household products
occupational settings
formed when CO is bound to Hb
Carboxyhemoglobin
Leads to hypoxia since O2 is not bound to Hb → affects heart and brain
Carboxyhemoglobin formation due to CO
one of the indication is cherry-red colored blood
Carboxyhemoglobin formation
routes of exposure to CO
Aspiration
Ingestion
CO intoxication if exposed through aspiration
pulmonary edema and shock
can lead to death
CO intoxication if exposed through ingestion
esophageal lesions and GIT lesions (perforation)
CAN LEAD TO:
hematemesis (vomiting of blood)
abdominal pain & shock (if there is chronic blood loss)
metabolic acidosis/alkalosis
T/F
Carboxyhemoglobinemia Symptoms depends on the carboxyghemoglobin formed
T
COHb (%) typical in nonsmoker
0.5
COHb (%) seen in smokers
5-15
COHb (%) having shortness of breath with vigorous exercise
10
COHb (%) having shortness of breath with moderate exercise
20
COHb (%) having severe headache, fatigue, impairment of judgment
30
COHb (%) having confusion, fainting on exertion
40-50
COHb (%) when there is unconsciousness, respiratory failure, death with continuous exposure
60-70
COHb (%) that is immediately FATAL
80
CoHb Tx
100% O2 therapy
ANTIDOTE for CO
Dilution (of substance)
METHODS for CO det.
Spot Plate Test
Differential Spectrophotometry
Gas Chromatography
How is spot plate test for CO det. performed?
5mL aqueous whole blood (1/20) + 5mL of 40% NaOH
Aqueous whole blood: prepared by diluting blood with water (1 part of blood per 20 parts volume of solution)
Add 5mL of 40% NaOH
Pink color solution = >20% COHb
Indication if there is >20% COHb in Spot Plate Test
Pink colored solution
Principle: Different forms of Hgb present with different spectral absorbency curves (6 diff. wavelengths)
Differential Spectrophotometry
Most commonly used method and basis of automated systems for CO det.
Differential Spectrophotometry
Principle: utilizes thermal conductivity by releasing carbon monoxide using potassium
ferricyanide
Gas Chromatography
an accurate and precise method (Ref. method) for CO
Gas Chromatography
Supertoxic substance
Cyanide
Cyanide may exist as
solid or gas
odor of the gas form of cyanide
Bitter almond odor
One of the most common suicidal agents (in the form of silver cleaners)
Cyanide
Used in many industrial processes
Cyanide
Insecticides and rodenticides component
Cyanide
Produced by pyrolysis of some plastics
Cyanide
Routes of exposure to cyanide
Inhalation
Ingestion
Transdermal absorption
route of exposure when one may be exposed to both cyanide and CO
smoke inhalation
blood component where cyanide may bind
heme iron
mitochondrial cytochrome oxidase
intoxication if Cyanide + heme iron
Hb can no longer bind O2 leading to hypoxia and anemia
intoxication if Cyanide + mitochondrial cytochrome oxidase
Inhibits mitochondrial cytochrome oxidase → increases cellular oxygen tension and venous partial O2 pressure
METHODS for cyanide det.
Ion-selective electrode
Photometric assay (two-well microdiffusion separation)
Urinary thiocyanate concentration
most commonly used methods for cyanide det.
Ion-selective electrode
Photometric assay (two-well microdiffusion separation)
test used in exposure to very low levels of cyanide
Urinary thiocyanate concentration
Some METALS AND METALLOIDS assessed in toxicology
Arsenic
Cadmium
Lead
Mercury
Pesticides
A metalloid that exists as a bound to or as a primary constituent of many organic or inorganic compounds
Arsenic
Binds to thiol groups in protein due to high affinity
Arsenic
Common homicidal & suicidal agent
Arsenic
Can cross the placenta
Arsenic
Arsenic intoxication
IV hemolysis
Hemoglobinemia
Nephrotoxicity
Multi-organ involvement
Indications of Arsenic intoxication
Garlic breath odor
Metallic taste
SPECIMENS used if there is short-term Arsenic exposure
Blood
Urine
SPECIMENS used if there is long-term Arsenic exposure
Hairs
Nail
*As loves to bind to keratinized tissues
METHODS for As det.
Atomic Absorption Spectrophotometry (AAS)
Reinsch test
Utilized in electroplating and galvanizing
Cadmium
Found in paints and plastics
Cadmium
Binds to proteins and cellular constituents
Cadmium
Cadmium Intoxication
Nephrotoxic
o Tubular proteinuria
o Glucosuria
o Aminoaciduria
Spx for Cadmium det.
Urine
Whole blood
merhod for Cadmium det.
AAS
Paints & make-ups color enhancer
Lead
Found in gasoline & pipe plumbing
Lead
Common water contaminant
Lead
Potent enzyme inhibitors
Lead
Mercury
Enzymes inhibited by lead
Delta-aminolevulinic acid (D-ALA) synthetase
Pyrimidine-5’-nucleotidase (P5’N)
Na-K ATPase
responsible for excess DNA removal in RBC nucleus
Pyrimidine-5’-nucleotidase (P5’N)
What will happen if Pyrimidine-5’-nucleotidase (P5’N) is inhibited by LEAD?
DNA accumulates inside the RBC causing basophilic stippling
Has high affinity to many macromolecular structures and distributed throughout the body; Present in all biologic system but has NO physiologic nor biochemical function
LEAD
has SLOW elimination through renal filtration
lead
reasons why lead has SLOW elimination through renal filtration
LOW Pb conc. in the blood
Pb combines with the bone matrix (hence, largest Pb conc. is in skeletal system): may persists up to 20 years
toxic dose of lead
> 0.5 mg/day
fatal dose of lead
0.5 g
toxic blood lvl of lead
> 70 ug/dL
Lead Intoxication
Anemia – Pb inhibits heme synthesis
Decreased RBC membrane integrity
Encephalopathy
Nephrosis
Anorexia
Peripheral neuropathy
Birth defects
Low IQ
Carcinogenesis
Renal damage
Indications of Lead intoxication
Basophilic stippling/ blueberry muffin-like RBC
Increased Urinary ALA
Free RBC protoporphyrin
sensitive indicator of Pb poisoning; due to inhibited P5’N
Basophilic stippling
this presence is due to Pb inhibiting multiple steps of heme synthesis
Free RBC protoporphyrin
Tx for lead intoxication
chelators
examples of chelators used for lead intoxication tx
EDTA
Dimercaptosuccinic acid (DMSA)
SPECIMENS used for Lead det.
Whole blood
Urine (recent Pb exposure)
Hair
spx used if there is RECENT lead exposure
urine
Methods for lead det.
- Screening
a. Zinc Protoporphyrin test (Fluorometric test)
b. Aminolevulinic acid dehydratase (ALAD) test - In-vivo X-ray Fluorescence of Bone
- AAS
- ICP-MS
- Anodic stippling voltammetry
sensitive method for Lead screening
Aminolevulinic acid dehydratase (ALAD) test
enzyme inhibited by mercury
Catecholamine-0-methyltransferase
Catecholamine metabolic enzyme (metabolizes epinephrine or norepinephrine)
Catecholamine-0-methyltransferase
unmetabolized catecholamines due to MERCURY presence may lead to
pheochromocytoma - tumor that autonomously produces catecholamines
reference value of mercury
<10 ug/dL
3 forms of mercury with different toxicity levels
elemental mercury
inorganic salts
component of organic compounds
value if there is significant exposure to Hg
> 50 ug/dL (whole blood)
Hg intoxication mimics these disorders
adrenal gland disorders (due to inhibited catecholamine metabolism)
Indicators of Hg intoxication
Hypertension
Tachycardia
Sweating
*these are pheochromocytoma symptoms
spx for Hg det.
Whole Blood
24h Urine
methods for Hg det.
Reinsch test
AAS
Anodic Stippling Voltammetry
Hg liquid at RT
Elemental mercury
Ingested but may not show significant effects (not absorbed)
Elemental mercury
Inhalation is very rare and insignificant (due to low vapor pressure
Elemental mercury
Elemental mercury intoxication
Pink disease (acrodynia)
Erethism
continuous skin exfoliation upon exposure until skin turns pink caused by elemental mercury
Pink disease (acrodynia)
moderately toxic form of Hg
inorganic salts
Hg form that is partially absorbed by the GI tract
inorganic salts
this form of Hg not absorbed shows GI tract toxicity
Inorganic salts
Inorganic salts (Hg) intoxication
Nephrotoxic (glomerular proteinuria)
Alkyl mercury intoxication
congenital Minimata disease
a neurologic disorder resembling cerebral palsy
congenital Minimata disease
Most toxic form of Hg; rapidly absorbed
component of organic compounds
ex. of Hg component of organic compounds
methylmercury
Substances intentionally added to the environment to kill/harm undesirable life forms
Pesticides
Pesticides can be classified as either
insecticides or herbicides
Forms of insecticides
Organophosphate
Carbamates
Halogenated Hydrocarbons
most common form of insecticide
Organophosphate
responsible for 1/3 of all pesticide poisoning
Organophosphate
forms of insecticides that inhibits ACETYLCHOLINESTERASE
Organophosphate
Carbamates
Muscle cell stimulant; stimulant of some endocrine and exocrine glands
Acetylcholine
Metabolized by acetylcholinesterase
Acetylcholine
what is the effect of Organophosphate and Carbamates in inhibiting acetylcholine metabolism?
cause systemic effects (since acetylcholine stimulates several parts of the body)
Effects of low level exposure to pesticides
Salivation
Lacrimation
Involuntary urination & defecation
Effects of high level exposure to pesticides
- Bradycardia
- Muscular twitching
- Cramps
- Apathy
- Slurred speech
- Behavioral changes
- Death (due to respiratory failure)
spx used for pesticides det.
RBC for AIA
Used for INDIRECT measurement of organophosphate poisoning
Acetylcholinesterase Inhibition Assay (AIA)
T/F
direct organophosphate poisoning measurement is highly possible
F
Direct organophosphate poisoning measurement is highly IMPOSSIBLE because of its high affinity to proteins
Alternative & Screening test for pesticides
Serum Pseudocholinesterase Activity
a method used for pesticide det. that lacks sensitivity and specificity
Serum Pseudocholinesterase Activity
methods for pesticide det.
Acetylcholinesterase Inhibition Assay (AIA)
Serum Pseudocholinesterase Activity
other conditions where Serum Pseudocholinesterase Activity may be decreased?
acute infection, pulmonary embolism, hepatitis, cirrhosis
alcohols that can cause metabolic acidosis
methanol
ethylene glycol
nephrotoxic metals and metalloids
arsenic
cadmium
inorganic Hg