Toxicology Exam 1 Flashcards
What is the governing agency that regulates pesticides?
EPA - environmental protection agency
What are the two major federal pesticide statuses regulated by the EPA?
FIFRA (federael insecticide, fungicide, and rodenticide act) - governs the sale and use of pesticide products in the US.
FFDCA (federal food, drug, and cosmetic act) - governs the limit of pesticide residues on food and feeds
What does the EPA determine?
Whether a “safe” level of pesticide residue, called a “tolerance” can be established before registration
The EPA specifies approved uses and conditions of uses, including what?
safe methods of handling (personal protection, ventilation, etc), storage, and disposal
must be explained on the product label - material safety data sheet
What are some natural sources of organochlorines?
through biological, physical, and chemical processes
- include bacteria, fungi, plants, marine organisms, insects, and other animals, to forest fires, volcanoes, and other geothermal events
- major sources include oceans followed by soil
what are some synthetic sources of organochlorines?
- chlorination modifies the physical properties of hydrocarbons in several ways resulting in a wide structural variety and divergent chemical properties that leads to a broad range of names and applications.
what are some chemical properties of organochlorines?
- persistent in the environment –> chlorination of the organic compounds reduces reactivity - results in increased size, decreased volatility, increased boiling point - MORE STABLE
- persistent in the environment!
- lipophilic
what are the two main groups of organochlorine pesticides?
DDT type compounds
chlorinated alicyclics (open and closed chains)
What was the effect of DDT on many birds?
- biomagnification
- eggshell thinning - estrogen like activity impairs the shell gland’s ability to excrete calcium carbonate to harden the shell
endocrine disruptor
what was an unintentional consequence of DDT use?
- DDT was used to reduce malaria in Borneo
- observed that thatched roofs were collapsing because DDT killed the wasps that ate thatch eating caterpilars
- dead wasps were eaten by lizards and then eaten by cats
- cats died as a result –> increase in rodents
- increase in rodent related diseases
- stop use of DDT
- CAT DROP to drop an excess of 20 cats in the area
Why were organochlorines developed?
to replace DDT (methoxychlor)
what are the uses of Methoxychlor?
used to protect crops, ornamentals, livestock, and pets against fleas, mosquitoes, cockroaches, and other insects
what was the problem with organochlorines?
Methoxychlor
- acute toxicity
- bioaccumulation
- endocrine disruption
Lindane (lice and scabies)
- banned by the EPA for agricultural use but still used for pharmaceutical use in humans and animals
how are animals exposed to organochlorines?
- label directions not followed
- concentrations miscalculates for sprays or dips
- contaminated feed or water
- packages or containers unsecured or unlabeled
- lack of appropriate PPE
How are organochlorines absorbed?
- dermal most common - damaged skin facilitates absorption
- inhalation and oral as well
What is the MOA of DDT-type organochlorines?
- neuronal membrane permeability or transport of Na and K is altered
- axonal Na channels remain open and K channels don’t open completely –> inhibits repolarization
- continued NT release
- hyperexcitability
what is the MOA of chlorinated alicyclic type organochlorines?
- binds to but doesn’t activate GABA receptors –> BLOCKS action of GABA (an antagonist)
- inhibits repolarization
- hyperexcitability
how are organochlorines metabolized/excreted?
- liver enzymes - most are dechlorinated (CP450), conjugated, and excreted in feces and urine
- biliary excretion is major route of decontamination (metabolites can enter enterohepatic recycling, be reabsorbed, and result in toxicity!)
- excreted in milk
what are the main clinical signs with organochlorines?
- CNS HYPERSTIM
- salivation, vomiting, weakness, incoordination, disorientation
- tremors, spastic gait, chewing, hyperthermia, muscle spasms
- tonic-clonic seizures, opisthotonos, coma, and death
- some mammals may show intermittent or persistent depression instead of CNS excitement
- birds may show depression, abnormal postures, blindness, death
how do we diagnose organochlorine toxicosis?
- no specific lesions
- secondary changes - trauma from convulsions, congestion/edema of organs
chemical analysis
- can confirm acute toxicosis if chemical in blood, liver,r or brain at high concentrations
What are the DDx with organochlorine toxicosis with swine?
- dehydration/Na imbalance
- pseudorabies
What are the DDx with organochlorine toxicosis with dogs and cats?
- strychine
- fluoroacetate
- lead
- organophosphate
- metaldehyde
- rabies
What are the DDx with organochlorine toxicosis with cattle?
- OP
- lead
- polioencephalomalacia
- infectious thromboembolic meningoencephalitis
- ketosis
- coccidiosis
What is the treatment for organochlorine?
no specific antidote
decontamination
- soap and water
- induce emesis
- cathartics
- activated charcoal
- IV fat emulsion
symptomatic treatments
- diazepam or barbiturates for seizures
- oxygen, ventilation, fluids
when is activated charcoal the most effective?
1-3 hours (effective up to 6 if toxicant has delayed release)
what is the MOA of organophosphates?
irreversibly inactivate acetylcholinesterase = persistent acetylcholine activity
what are the common exposure routes for organophosphates?
- contaminated feed or drinking water
- use of empty pesticide containers for feeding/watering animals
- dusting, spraying of animals or animal grounds or housing
- sheep dip
- flea treatment, meds
- overdose
- intentional poisoning
Why are organophosphates more toxic after 1-2 years in storage?
subject to storage activation
are organophosphates lipo or hydrophilic?
lipophilic - readily absorbed through the skin and mucus membranes, GIT, and inhalation
how are organophosphates normally metabolized?
in liver - excretion/bioactivation
Which organophosphate requires lethal synthesis?
thiophosphate
- liver enzymes (CYP450) metabolize or bioactivate
what can happen with continued low dose/chronic exposure of OPs?
- can lead to adaptation to decreased acetylcholinesterase - homeostatic response
- enzyme induction or increased acetylcholinesterase production
- receptor down regulation or decrease in acetylcholine receptor
thiophosphates are biologically inactive until transformed by?
the liver to -oxon metabolites
what is the major route of elimination for thiophosphates?
paraoxonase - a serum bound enzyme –> hydrolysis of paraoxon
what is the MOA of OPs? (plus primary - tertiary)
Irreversible inhibition of cholinesterases! (end result = increase in acetylcholine!)
- OP binds to cholinesterase
- aging = conformational change in OP-AChesterase complex that results in increased or irreversible binding of complex over time
primary: muscarinic receptor over stimulation
seconary: nicotinic receptor over stimulation (neuromuscular and CNS stim)
tertiary: nicotinic blockage (neuromuscular blockade, CNS depression)
what is the result of high exposure with OPs?
paralysis of diaphragm leading to pulmonary edema, asphyxia, and death due to respiratory failure
delayed neurotoxicity is possible with what OP?
thiophosphates
“OP induced delayed polyneuropathy”
what are the muscarinic effects of OP toxicity?
DUMBELLS
- diarrhea
- urination
- miosis
- bronchospasm
- emesis
- lacrimation
- salivation
what are the nicotinic effects of OP toxicity?
- ACh accumulation at the neuromuscular junction ans preganglionic synapses
- there are initial stimulations and muscle fasciculations followed by paralysis due to nicotinic block
- stimulation of the SNS may produce sweating, hypertension, and tachycardia
what are the CNS effects of OP toxicity?
- cross the BBB
- increase sensory and behavioral distrubances, incoordination, depressed motor function, and resp depression
- resp paralysis
- increased pulmonary secretions coupled with resp failure = USUAL CAUSE OF DEATH
what is the normal cause of death in a patient with OP toxicity?
- increased pulmonary secretions coupled with respiratory failure
what is OP-induced delayed polyneuropathy?
- develops 10-14 days after exposure
- distal degeneration of long/large diameter motor and sensory axons of peripheral nerves and spinal cord
- clinical signs = muscle weakness, ataxia, rear limb paralysis
- chickens most sensitive
what is OP-induced intermediate syndrome?
- occurs 204 days after acute cholinergic effect and signs of the acute effects are no longer obvious
- symptoms and signs occur after apparent recovery from acute effects
- NO muscarinic signs or muscle fasciculations
- weakness of resp muscles and accessory muscles
what is the pathology of OP toxicity?
- acute death, no specific lesions
non specific lesions
- pulm edema
- congestion
- cyanosis
- hemorrhages
- edema of various organs
- necrosis of skeletal muscle
delayed effects: degeneration and demyelination of peripheral and spinal motor neurons
what lab diagnosis can we use for OPs?
- plasma achetylcholinesterase activity level
- <50% is suspicious, <25% is diagnostic!
what test can we run to see if an animal has been exposed to OPs?
atropine response test
- if the test is POS (dry MM, increased HR, dilated pupils) = LOW LIKELY OP poisoning!
- if the test is NEG (no signs seen) = LIKELY OP POISONING
how do we generally treat OP poisoning?
- decontaminate
- if dermal, wash gently
- if ingested and RECENT, induce emesis but NOT if resp is depressed of if there are seizures
- if ingested, give activated charcoal - supportive care
- rest, nutrition, ventilation, O2 therapy - avoid phenothiazines, aminoglycosides, muscle relaxants, and drugs that depress the respiration (opioids)
what DRUG do we use to treat OP poisoning?
Atropine
- specific ACh
antagonist
- repeat with decreasing doses 3-6 hours based on clinical response
what is the main goal for atropine therapy with OP poisoning?
to suppress or dry pulmonary secretions
main concern with OP tox is resp failure from excessive airway secretions
How can we treat OP poisoning with 2-PAM?
- it is a cholinesterase reactivator - “oximes”
- binds to OP-inactivated acetylcholinesterase and reverses the binding
Carbamate pesticides are derived from?
carbamic acid
What was the first successful carbamate insecticide?
Carbaryl
- broad spectrum of insect control
- very low mammalian, oral, and dermal toxicity
- outdoors - used as a lawn and garden insecticide
- indoors - used in sprays or baits in the control of pests
what is the MOA of Aldicarb?
- mimics the structure of acetylcholine
- MOST TOXIC Carbamate
do carbamates undergo storage activation?
NO
what are the toxicokinetics of carbamates?
- do not penetrate the CNS - effects are mostly resp
- do NOT require hepatic bioactivation (most toxic than some OPs in very young patients)
- faster onset and shorter duration than OPs
what is the MOA of carbamates?
- REVERSIBLE inhibition of acetylcholinesterase (competitive inhibition)
what are the clinical signs associated with Carbamate poisoning?
- similar to OP toxicity
- SLUD (salivation, lacrimation, urination, diarrhea)
- death results from resp failure and hypoxia due to bronchoconstriction leading to tracheobronchial secretion and pulmonary edema
what is the main drug treatment for carbamate poisoning?
atropine!
are oximes or 2PAM effective against carbamates?
no - reversible binding reduces benefit
Naphthalene is the toxic component of what household item?
mothballs
how many mothballs can cause a toxic reaction in dogs/cats?
just one can be highly toxic!
- 400 mg/kg lowest canine lethal dose
how are animals exposed to naphthalene?
- absorbed through inhalation, orally, dermally, vapor (eye irritation)
- won’t really be absorbed until it hits the intestine if eaten
- people keep moth balls in closet
how does pH affect the absorption of naphthalene?
- acids delay
- bases enhance
it is lipid soluble so the oils increase skin and GI tract absorption
where can we find high concentrations of naphthalene in the body?
- fat, kidneys, liver, lungs
why is naphthalene a risk for fetuses and neonates?
- crosses the placenta
- excreted in milk
how is naphthalene metabolized?
- metabolized in the liver by hepatic enzymes (CYP450)
- metabolites can for epoxides or quinones - reabsorption may cause cellular damage
- metabolites can be conjugated with glutathione to non-toxic substances
- metabolites can be conjugated with sulfate, glucoronic, or mercapturic acid for excretion
how is naphthalene excreted?
primarily through urine but also bile
what is the MOA of naphthalene?
- the oxidative metabolites (oxides) in the circulation can cause hemolysis and methemoglobinemia
- effect is cellular/tissue hypoxia
what are the main clinical signs with naphthalene?
- salivation
- vomiting
- mothball scented breath
- pale or brown gums
- methemoglobinemia, hemolytic anemia, hemoglobinuria
- weakness or lethargy
- labored breathing
- tremors and seizures
what are some changes we can see in the blood with naphthalene toxicity?
- hemolysis, heinz bodies
- methemoglobinemia (blood is chocolate brown)
- hemoglobinuria
what can we use to treat severe cases of naphthalene poisoning?
methylene blue 1%
- reduces methemoglobin to hemoglobin
- make sure to use correct dose
- controversial in CATS - can case hemolysis
how is nicotine absorbed?
- readily through MM and resp tract - caustic
- absorption in GIT –> acids delay/bases enhance absorption
what dose of nicotine are clinical signs reported?
1mg/kg
*cigars have 45-150mg
how is nicotine metabolized/excreted?
- liver readily extracts nicotine from circulation
- two principal oxidative metabolites (cotinine and nicotine oxide)
- metabolites are inactive and extracted by the kidneys and excreted in urine
- -> renal excretion is decreased in alkaline or high pH - increased reabsorption
- -> renal excretion increased in acidic or low urine pH
what is the MOA of nicotine?
- potent PSNS stimulation
- cholinergic receptor agonist
- at low doses -> mimics acetylcholine and stimulates post synaptic nicotinic receptors
- at high doses –> stimulation will be followed by blockage
- stimulates CRTZ –> vomiting
what are the clinical signs associated with nicotine?
- early stimulation (ganglionic and neuromuscular)
- ataxia
- lethargy
- bradycardia
- tremors - later (or with high doses) nicotinic blockade
- CNS depression
- tachycardia
- vasodilation
- paralysis of resp muscles = RESP FAILURE
how do we treat nicotine poisoning?
- decontamination
- induce emesis/lavage
- activated charcoal
- AVOID antacids, which increase pH and DECREASE excretion/INCREASE GI absorption - enhance excretion
- diuretics/IV fluids
- lower pH of urine - atropine for parasympathetic effects
- diazepam to control seizures
what are some properties of neonicotinoids?
- water soluble
- degrades slowly in the environment
- degraded by direct light
- charged nitrogen metabolites (toxic to non target species)
what are the toxicokinetics of neonicotinoids?
- poorly absorbed
- metabolized in liver
- excreted in bile and urine
what is the MOA of neonicotinoids?
- ACh receptor agonist - binds to nicotinic receptor
- bind ACh-esterase (binding is irreversible - OPs too)
- high levels of ACh agonist and neonic-induced inhibition of cholinesterase results in overstimulation, paralysis, DEATH
neonicotinoids cannot cross the BBB in what animals?
mammals!
can cross in insects
what is rotenone only approved for as a use?
piscicide
- used by fish managers to kill unwanted fish in rivers and lakes - NOT SPECIES SPECIFIC - repopulation needed!
explain the exposure routes and metabolism of rotenone
- it is readily degraded upon exposure to warm air and light
- more LIPOphilic than hydrophilic
- GIT and dermal absorption is LOW and incomplete UNLESS mixed with fats/oils
- inhalation is more toxic - direct pathway to circulatory system
- metabolized in liver and excreted in feces/urine within 24 hours
rotenone is highly neurotoxic to what animals?
- fish and arthropods
what is the route of exposure with rotenone?
through the gills or trachea
- resp mechanism of fish directly linked to water
- rotenone passes directly into the bloodstream through the gills and is converted to highly toxic metabolites in the LIVER
why isn’t rotenone highly toxic to mammals and birds?
- route of exposure is normally through the gut
- rotenone is readily broken down to less toxic metabolites before toxic quantities can enter the blood stream
what is the MOA of rotenone?
- blocks oxidative phosphorylation in the citric acid cycle
- interferes with the electron transport chain/ATP production in mitochondria
- cellular oxygen is reduced, resulting in reactive oxygen species (ROS)
- ROS can result in oxidative stress, damaging DNA and organelles resulting in neuronal death –> NEUROTOXICITY
What are the clinical signs with rotenone toxicity?
- dermal exposure
- local irritation such as conjunctivitis, congestion, dermatitis - oral exposure
- GIT irritation, convulsions, muscle tremors, lethargy, incontinence, and resp stimulation followed by resp depression - resp exposure
- severe pulmonary irritation and asyphyxia
Generally as a neurotoxin, depression and convulsions are the main CS
what lab results might we see antemortem with rotenone toxicity?
- hypoglycemia
- liver enzyme changes
- hypoxemia/hypercapnia