Exam 1 - Insecticides Flashcards
What are the insecticides?
Pyrethrins and Pyrethroids
DEET
Amitraz
Ivermectin
What are pyrethrins and pyrethroids?
Pyrethrins are extracts of pyrethrum flowers
Pyrethroids are synthetic analogs of pyrethrins
T/F Pyrethrins and pyrethroids are very unstable in air and light, break down quickly
True
T/F the overall toxicity to mammals and fish is high with pyrethrins and pyrethroids,
False - overall low toxicity to mammals (no subacute or chronic form, generally acute, mild toxicity)
Very toxic to fish and some birds
How could a fish pond get exposed to pyrethrins and pyrethroids?
If your canine has a topical product and goes swimming in the pond
T/F - dogs are more sensitive to pyrethrins/pyrethroids than cats
False - cats are more sensitive than dogs. Use of canine “spot on” products on felines is a common presenting issue
Are pyrethrins lipid or water soluble?
lipid
What is the route of exposure with pyrethrins/pyrethroids?
dermal most common
Ingestion and inhalation possible
Do pyrethrins and pyrethroids accumulate in tissue and have residual effects?
no
What does piperonyl buttoned or MGK-264 do when added with pyrethrins/pyrethroids?
Have a synergist effect. Inhibit pyrethrin metabolism by insects
Not supposed to have a significant effect in mammals
What is the MOA of pyrethrins/pyrethroids?
Delay closure of sodium ion channels in the axonal membrane of the insect
“knockdown effect” rapid paralysis caused by inhibition of neurons
What type of pyrethroids have a greater effect on sodium channels?
Type y pyrethroids (alpha-cyans group)
Pyrethrins and pyrethroids may stimulate the adrenals which may result in
hyperglycemia
What is the difference between insects and mammals that pyrethrins and pyrethroids affects them most?
Pyrethrins bind more strongly at lower temps
Insect Na channels are 1000x more sensitive
Insect Na channels dont recover from depolarization as quickly
Insect metabolism of pyrethrins is slower
What clinical signs will you see with pyrethrin and pyrethroid toxicity?
Muscle tremors, depression, blindness (reversible), ataxia, salivation, vomiting, diarrhea, hyperexcitability, seizures, dyspnea, death
it is difficult to diagnose an animal with pyrethrins/pyrethroid toxicity, however, postmortem the best tissues are
Liver and brain
How could you treat pyrethrin/pyrethroid toxicity?
no specific antidote
Wash skin with soap/water (careful because hypothermia may lead to prolong clinical signs -slow Na channel kinetics)
T/F Activated charcoal could be used in pyrethrin/pyrethroid toxicity
False - its generally not used - causes too much stress
What drug could you use to treat severe muscle tremors in an animal with pyrethrin/pyrethroids toxicity?
Methocarbamol
What drugs could you use to treat seizures in an animal with pyrethrin/pyrethroid toxicity?
Diazepam, barbiturates, propofol CRI
What is the prognosis for an animal with pyrethrin/pyrethroid toxicity?
Generally very good
What is a common insect repellant used for control of mosquitoes, flies and ticks?
DEET
What may deet damage?
Synthetic fibers or plastics
Dogs and cats are susceptible to deet, but which one is more sensitive?
Cats and young animals
What may increase the toxicity of Deet?
CNS depressants
Does Deet have cumulative effects?
Yes, can accumulate and persist in the skin
What could Deet do to the absorption rate of other drugs, such as fenvalerate and pyrethroid?
Increase dermal absorption
What is the MOA of Deet?
Unknown, can cause surface irritation
what clinical signs would you see with Deet toxicity?
Hypersalivation, vomiting, hyperexcitability, tremors, ataxia, seizures
How could you diagnose Deet toxicity?
no specific pathologic lesions
Chemical analysis - stomach, urine, blood, skin, vitreous, bile, kidney
How many ppm are considered diagnostic for Deet toxicity?
20ppm
Urine concentration of greater than 1 ppm and tissue greater than 10 ppm considered supportive
What are your ddx for deet toxicity?
other CNS excitatory toxins Strychnine Metaldehyde Organochlorine OP/carbamate
How could you treat Deet toxicity?
No specific antidote
Decontamination - wash/soap, emesis if not contraindicated, activated charcoal +/- cathartic
What should you avoid giving an animal with Deet toxicity?
Magnesium cathartics - may cause CNS depression
What is the prognosis for an animal with Deet toxicity?
If sublethal exposure, usually response in 24-72 hrs.
What is a foramidine insecticide/acaracide?
Amitraz
Amitraz is particularly useful for certain mites and ticks, what does it do to them?
Paralyzes the mouth parts
Where might you find amitraz in ?
Flea and tick collars (preventic)
Mitaban
As a miticide/insecticide for swine and cattle
Plant insecticide
What animals should you not use amitraz on?
Cats and horses
What is the MOA for amitraz?
Alpha 2 adrenergic agonist in the CNS
Weak alpha 1 agonist activity
Weak monoamine oxidase (MAO) inhibitor
Amitraz toxicity may be acute or subacute, what is the acute oral LD50 for dogs?
250mg/kg
What increases the toxicity of amitraz?
Meperidine (Demerol)
Sympathomimetic amines
Stress, debilitated, old age, toy breeds
How is amitraz absorbed?
Orally, inhalation or skin
What is the peak plasma concentration time of amitraz and elimination half life?
5 hours
1/2 life of 24 hrs
What clinical signs will you see with amitraz toxicity?
Transient sedation in seen and may last for 24-72 hrs
Lethargy, ataxia, bradycardia, depression, vomiting, dyspnea, hypothermia, tremors, seizures
Cardiovascular collapse and Resp. failure
What can the alpha 2 inhibition of amitraz cause?
Hyperglycemia - alpha 2 inhibition of insulin
How could you diagnose Amitraz?
no specific pathologic lesions
Tissue analysis. liver, kidney, brain, adipose
What are your ddx for amitraz toxicity?
Other CNS depressants Ethanol Ivermectin Ethylene glycol marijuana
How could you treat amitraz?
Alpha 2 antagonists Yohimbine Atipamezole (fewer cardioresp. effects than yohimbine) Washing/soap Emesis/activated charcoal/cathartics Supportive care (IV fluids)
What is the prognosis for amitraz toxicity?
Pretty good
What are macrocytic lactones?
Avermectins (Ivermectin, selamectin, moxidectin)
Milbemycins
Ivermectin is a common
Endoparasiticide
Ivermectin labeled for prevention of ____ in dogs and cats
Heartworm
What breed of dogs are most susceptible to ivermectin toxicity? why?
Collies - ABCB1/MDR1 mutation
T/F Ivermectin is well absorbed orally, oral absorption is more rapid than SC, its well distributed but does not typically cross the BBB, and dogs may have a lower bioavailability than cats
False - cats may have lower bioavailability than dogs. all else is true
Why does ivermectin not cross the BBB?
kept out of the CNS by p-glycoprotien efflux pump
What is the elimination half life of ivermectin in normal dogs?
2 days
Why is the ABCB1/MDR1 gene important?
It encodes the p-glycoprotein which is a component of the BBB (keeps drugs out)
What is ivermectin MOA?
Acts as GABAa agonist - influx of chloride ions hyper polarizes the cell decreasing firing of the neuron (CNS suppression)
What occurs in overdose situations of ivermectin?
Binding to glycine and voltage gated chloride channels
What may low concentrations of ivermectin cause?
may reduce GABA and cause excitatory signs
What clinical signs will you see with ivermectin toxicity?
CNS depression - disorientation, stupor, ataxia, hyperesthesia, hypersalivation, vocalization, progressive weakness, recumbency, coma and death.
Mydriasis, cortical blindness, hypothermia, vomiting, drooling, seizures
What are your ddx for ivermectin toxicity?
Other CNS depressants Ethanol Methanol ethylene glycol amitraz
How would you treat an animal with Ivermectin toxicity?
NO specific antidote
Emesis if not contraindicated
Activated charcoal (more useful than emesis)
Physostigmine (cholinesterase inhibitor)
Supportive care
What should you be cautious with when treating Ivermectin toxicity?
GABA agonists (diazepam, barbiturates, propofol)
What therapy would be useful for fat soluble toxins?
Intravenous lipid emulsion (ILE)
What is lipid emulsion composed of?
Triglycerides and phospholipids
What fat soluble toxins will intravenous lipid emulsion help with?
Chlorinated hydrocarbons (organochlorines)
Pyrethrins?
Ivermectin
Ionophores
Marijuana, “spice”
Drugs: baclofen, bupivacaine, calcium channel blockers
How does IV lipid therapy (ILE) work?
Forms chylomicrons in the serum which trap toxins and act as a ‘lipid sink’ for the toxin
May enhance myocardial function
How might IV lipid therapy help myocardial function?
FFAs are preferred energy source for myocardiocytes - Increased FFA stimulate activation of voltage gated calcium channels, increase cytosolic Ca+ and increase cardiac function - beneficial in certain toxins (calcium channel blockers)
What are potential adverse effects of ILE therapy?
Bacterial contamination - sepsis
Pyrogenic reaction (fever)
Fat embolism, hyperlipiemia, hepatomegaly, icterus, splenomegaly, thrombocytopenia, hemolysis, neuro signs
What animals should you avoid ILE therapy in?
Pigs! hypersensitivity reactions
