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Toxicology VAP845 > L10. OP, Carbapenems, Pyrethrins > Flashcards

L10. OP, Carbapenems, Pyrethrins Flashcards

1
Q

Insecticide:

Sources

A
  • Accidental incorporation in feed
    • unintended application to crops/forages
    • mistaken for feed ingredients
  • Mis-use/mis-calculation for use
    • sprays, dips, pour-ons, collars
    • Unintended species
  • Low-level chronic exposure
    • cumulative exposure to persistent chemicals
  • Accidental Access
    • storage areas, garbages
  • Malicious Poisoning
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2
Q

Insecticide:

Considerations

A
  • Formulations
    • liquids vs granulars vs powders
  • Toxicity
    • inherent toxicity
  • Intended Use
    • crop vs. animal products
    • Crop products generally more potent and combined with solvents
  • Restriced use pesticides
    • extreme toxicity, long residual effects, special applications
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3
Q

Chlorinated Hydrocarbons

A
  • Higly lipid soluble
    • fat and brain
  • Persistent in Environment
    • resist degradation
  • Bioaccumulate
    • repeat exposures
  • Largely removed from market
    • environmental concerns
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4
Q

Chlorinated Hydrocarbons:

Sources

A
  • Mostly off market
  • Old products still exist
    • DDT, Chlordane, Dieldrin, Aldrin, Toxaphene
  • Accidental access to old storage buildings
  • Occasional intentional poisoning
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5
Q

Chlorinated hydrocarbons:

Toxicokinetics

A
  • All aminals susceptible
  • Typical routes of exposure
    • oral, topical, inhalation
  • Lipid soluble
    • rapid absorption
  • Distribute to liver, kidney, brain, fat
  • Metabolism by mixed function oxidases to more toxic epoxides
  • Accumulate in brain, fat
  • Excreted in bile and milk fat
  • Released to blood during weight loss
    • can cause bimodal progression of signs
    • Toxicosis after some toher issues
  • Excretion half life may have two compartmsents
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6
Q

Chlorinated Hydrocarbons:

MOA

A

Lowers action potential thersholds

Especially in CNS

Affects GABA receptors; similar to strychnine

  • Diphenyl aliphatics (DDT)
    • interfere with Na+ flow in nerves
    • Lowers threshold for action potential
  • Cyclodienes
  • Inhibit postsynaptic binding of GABA
    • lowers thershold
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7
Q

Chlorinated Hyrdrocarbons:

Toxicity

A

Cast most sensitive - LD50 3-6mg/kg

Dog - LD50 50-65mg/kg

Cattle minimun toxic dose - 1–25mg/kg

Lindane for ectoparasites in dogs has potential for iatrogenic or accidental exposure

Cats - LD50 25mg/kg

Dogs - LD50 40mg/kg

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8
Q

Chlorinated Hydrocarbons:

Clinical Picture

A
  • Acute onset 12-24 hours
    • Behavioral Changes
      • hypersensitive, belligerent, walking backwards
    • Muscle Tremors
      • expecially head, face, neck
    • Tono-clonic convulsions
      • intermittent CNS depression
      • Almost appear normal between episodes
      • Death due to respiratory failure
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9
Q

Chlorinated Hydrocarbons:

DIagnosis

A

Clinpath not helpful

Acute toxicosis: measure residues in GI content, brain, liver

No specific lesions or no lesions at all

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10
Q

Chlorinated Hydrocarbons:

Treatment

A
  • Treat the patient not the poison
  • Symptomatic:
    • control seizures - diazepam, phenobarb
    • Activaed charcoal and cathartics
    • Wash with soap and water if dermal exposure
  • Pronosis vairable based on exposure
  • Consider environmental persistance
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11
Q

Chlorinated Hydrocarbons:

Environmental and Food Safety

A

All aniamls species are targets

Potential for relay intoxication exist

Eggshell thinning in birds - DDT

Bio magnification

Food safety impact

Residues awarness and restricitons

Reportable disease: report to public helath or FDA

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12
Q

Pyrethrins – Pyrethroids

A
  • Pyrethrins:
    • extracts of Chyrsanthemum
    • Not very stable in the environment
  • Pyrethroids
    • synthetic, stable
    • Permethrin, cypermethrin, fenvalerate
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13
Q

Pyrethrins - Pyrethroids:

Source

A

Quick nock down fly spray

premise fly control products

Many dips, spot ons, sprays, shampoos, ear tags, crop sprays

Ready to use generally < 2% active ingredient

Spot on products 40-65% concentration

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14
Q

Pyrethrins - Pyrethroids:

Type 1

A

Allethrin

Permethrin

Phenothrin

Resmethrin

Sumithrin

Telfuthrin

Tetramethrin

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15
Q

Pyrethrins - Pyrethroids:

Type 2

A

Cytluthrin

Cyhalothrin

Cypermethrin

Deltamethrin

Fenvalerate

Flumethrin

Fluvalinate

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16
Q

Pyrethrins - Pyrethroids:

Type 1 vs Type 2

A

Decamethrin - Type 2

Permethrin - Type 1

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17
Q

Pyrethrin - Pyrethroids:

Toxicity

A

Most quite safe, not very toxic

Toxicity enhanced by synergists

Oral toxicity is very low

Exposure is through the skin or by inhalation

Use of dog products on cats

Permethrin type 1 has high risk in cats

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18
Q

Pyrethrin - Pyrethroids:

MOA

Type 1

A

Slow the opening and closing of neural sodium and Potassium and Chloride channels

This lowers the threshold for firing of nerve and extends the action potential

CNS stimulation, muscle tremors, excitement

19
Q

Pyrethrin - Pyrethroids:

MOA

Type 2

A

Membrane depolarization predominates

Affect GABA channels

Tendency to weakness, paralysis

20
Q

Pyrethrin - Pyrethroids:

Clinical Picture

A

Onset often <1hr

Hyper excitable, tremors, seizures, ataxia, vomiting,

Some products (Type2) include more salivation, weakness, abnormal posture

Clinical poisoning usually goes to recovery (rarely death) in 24-72 hrs

Topical allergic pruritus, hyperemia, urticaria, dermatitis not uncommon

21
Q

Permethrin in cats

A

Highest risk for pyrethroid intoxication

  • Toxicosis has occured form contact with spon on treated dogs
  • Onset 2 min - 3 hrs
  • Hypersalivation, vomiting, seizures, paw shaking, ear twitching, flicking of tail, twitching of dorsal skin
  • Agitation, seizures can occur in 12-24 hrs post exposure
  • Seizures may be difficult to control
22
Q

Pyrethrin - Pyrethroids:

Diagnosis

A

History of exposure

General lab tests - increased PNMs, glucose

Chemiacla analysis - brain, skin

Analysis shows presence not peak concentration

23
Q

Pyrethrin - Pyrethroids:

Differenctial Diagnosis

A

Organic Phosphates

Cl-HC

Metaldehyde

Nicotine

Strychnine

24
Q

Pyrethrin - Pyrethroids:

Treatment

A

Discontinue exposure, control the tremors, general supportive care

Bathe with detergent

Methocarbamol for tremors

Alternatively use valium or pentobarbital

Supportive care : gluids thermoregulations

Check for hypoglycemia and treat as needed

Most animals recover in 24-72 hrs

25
Q

Pyrethrin - Pyrethroids:

Environmental and Food Safety Impact

A
  • Fish are extremely sensitve
    • shut off tank pump, cover air intake and tank during spraying or fogging in the home
    • Toxicity to toher cold blodded species??
  • Birds considered relatively resistant
  • Exotic species - little safety information
  • Food Safely: fencvalerate, cypermethrin, flucythrinate have possible residue concerns
26
Q

Organophosphate and Carbamate Insecticides:

Background

A

Part of a massive and diverse family of compounds

Commonly used in agriculture, home, and gardens since 1970s

Highly lethal

Chemical warfare agent

27
Q

Organophosphate and Carbamate Insecticides:

Sources

A

External parasite products

Both large and small animals

Agriculture

Home garden insecticide

28
Q

Organophosphate and Carbamate Insecticides:

Chemical Structure

A
  • OP → aliphatic, cyclic, or heterocyclic esters of phophoric acid
  • OPs have P=O bond adjacent to the ester
  • Organothiophophates have a P=S group
    • more stable in environment
  • P=O is more toxic
  • Oxidative desulfuration (P=S → P=O)
    • increases toxicity
  • Phase 1 mixed funciton oxidases
    • lethal synthesis
29
Q

ADME

A
  • Absorption rapid and complete
    • oral, dermal, inhalation routes
  • Distributed in plasma → liver → CNS
  • Metabolized by MFO system
    • deactivated by hydrolysis
  • Excretion of metabolites in urine and feces
30
Q

Organophosphate and Carbamate Insecticides:

Toxicity

A

Some have LD50s less than 10mg/kg

  • Susceptible animals
    • all
    • cats are more susceptible than dogs
    • Brahman cattle are more susceptible than English
    • Bull or other males are more susceptible than females
    • Poultry very susceptible to dichlorvos
31
Q

Organophosphate and Carbamate Insecticides:

MOA

A

Inhibit acethycholinesterase at cholinergic synapses

Allows for continuous stimulation by accumulated asetylcholine

Signs reflect stimulaiton of parasympathetic nervous system and neuromuscular juncitons

Muscarinic - SLUD syndrome

Nicotine - Tremors, ataxia, paralysis

32
Q

Organophosphate and Carbamate Insecticides:

Clinical Picture

A
  • Acute onset - minutes to hours
  • Parasympathetic stimulation → muscarinic
    • emesis, salivation, lacrimation, urination, defecation, chornoconstriction, miosis, bradycardia
  • Neuromuscular → nicotinic
    • Muscle tremors, stiffness, paralysis
  • CNS
    • apprehension, nervousness, seizures
  • Death form respiratory failure
33
Q

Organophosphate and Carbamate Insecticides:

Diagnosis

A
  • Clinical Signs:
    • acute onset, rapid death
  • History of exposure
  • Cholinesterase activity
    • blood, brain, retina acceptable
    • Carbamage exposure regeneration to normal
  • Chemical analysis
    • detection of parent compound
      • GI content, hair, bait ro any other suspect material
34
Q

Organophosphate and Carbamate Insecticides:

Toxic Differentials

A

Chlorinated pesticides

Strychnine

Pyrethroids

Zinc phosphate

Nicotine

35
Q

Organophosphate and Carbamate Insecticides:

Treatment

A
  • Atropine sulfate
  • Atropine loses efficacy after 2-3 doses
  • Do not over atropinize
  • Can be used in horses but extreme caution
    • GI stasis → colic
  • Glycopyrrolate - alternative to atropine
    • does not cross the blood-brain barrier
  • Oral activated charcoal, may be used as the only Tx in ruminants
  • Reactivator oximes
    • must give before aging
    • AChE irreversible binding
  • Not for carbamates
    • they spontaneously hydrolze
  • Dermal
    • wash with soap and water
36
Q

Organophosphate and Carbamate Insecticides:

Chlorphyriphos

A

Dursban: topical insecticide

Lorsban - crop insecticide

Cats → intermediate syndrome

Very sensitive, protracted course

Not labeled for cats

Signs: delayed 1-5 days

37
Q

Organophosphate and Carbamate Insecticides:

Environmental and Food Safety Impact

A

All animal species are targets

cats, fish, birds most sensitive

Secondary intoxications reported

Food safety impact

Do NOT eat

38
Q

Amitraz

A
  • Formamidine insecticide:
    • topical for controlling ticks, keds, lice, and mites
    • Mitaban - for topical use on dogs
    • Taktic - mites, lice, ticks on livestock
    • Preventic - collars for dog tick control
39
Q

Amitraz:

Mechanism

A

Acts as an alpha 2 adrenergic agonist

GI stasis, bradycardia, depression, increased blood glucose, sedation

Rapid oral absorption, plasma peak = 5 hrs

Half life = 24 hrs

40
Q

Amitraz:

Clinical Signs

A
  • Signs are dose related
    • onset within 2-4 hours
  • At therpeutic doses
    • transient sedation of 2-6 hr duration
    • Mild GI signs
      • anorexia, vomiting, diarrhea may be seen
  • Poisoning more likely
    • old, debilitated, diabetic
  • With higher doses
    • CNS depression
      • ataxia, mydriasis, hypthermia, hyperglycemia, bradycardia, hyptension, muscular weakness, emesis, uncontrolled vocal spasm, and mictruition have been noted
  • In horses - COLIC from GI stasis - may be fatal
41
Q

Amitraz:

Diagnosis

A

History of exposure

Campatible clinical findings

Hyperglycemia may be suggestive

Chemical detection: stomach content, urine, feces, tissues, blood, skin

Detection only confirms exposure

42
Q

Amitraz:

Treatment

A
  • Therapeutic dose:
    • no treatment needed
  • In overdose:
    • bathing for topical exposure
    • Emetics, gastric lavage or activated charcoal for ingestion
  • In dogs:
    • yohimbine reverses bradycardia, depression, repeat as needed
    • Atipamezole: fewer side effects than yohimbine
  • Supportive care
43
Q

Amitraz:

Environmental and Food Safety Impact

A

Several animal species are targets

Minimal relay toxicosis

Food safety impacts??

Toxicology VAP845 (15 decks)

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