Flashcards in Parasiticides TY Deck (57)
Why do parasiticides that affect chloride channels do not affect mammals?
Mammals do not have glutamate gated chloride channels
Do not cross the BBB
What are the two types of post synaptic cholinergic receptors?
Muscarinic and nicotinic
What is the MOA of organophosphates?
Irreversible inhibition of acetylcholinesterase (enzyme that breaks down acetylcholine in the neural synapse)
Mimics acetylcholine and inactivates enzyme at post-synaptic membrane
What are the signs of cholinesterase toxicity?
Acute: Rapid muscarinic signs, SLUD, Bradycardia, miosis; Nicotinic signs: Muscle stiffness, tremors, weakness; CNS signs; Death
Delayed: Not assoc w/ ACHe inhibition; OP ester induced delayed neuropathy; Onset 7-21 d
Chronic: like acute, rarely causes death
What are some examples of cholinesterase inhibitors?
Carbamates- reversible inhibition
Organophosphates- IRREVERSIBLE inhibition
What are the treatments for cholinesterase toxicity?
Atropine (muscarinic effects only)
2-PAM (prolidoxime)- frees AchE enzyme (OPP only)
What class of drug does fipronil belong to and what is its MOA?
GABA receptor antagonist (γ-aminobutyric acid)
Interferes with the passage of chloride in GABA regulated channels
What species has a toxic reaction to fipronil?
What ticks have shown resistance to fipronil?
5 spp of cattle ticks
What is the MOA of metaflumazone?
Blocks influx of Na+ required to propagate a nerve impulse along axon/dendrite of neuron
What is the MOA of amitraz?
Formamidine (Promeris, Preventic, Mitaban)
• a2 adrenergic activity, inhibits PG synthesis
• Can increase in plasma glucose by inhibiting insulin release via its alpha2-adrenergic activity
What are the side effects/precautions to consider with amitraz?
Transient sedation (~24 h, up to 72h), pruritus, hypothermia, bradycardia, hypotension, hyperglycemia (DIABETICS), ataxia, VD, edema, erythema and rarely seizures have been reported; toy breeds may be more susceptible – use ½ dose
Drug is unstable and rapidly oxidizes on exposure to air and sunlight; more toxic
Do not use with deep pyodermas with drainage tracts
What species have toxic reaction to amitraz?
Cats and rabbits
How do you treat amitraz toxicity?
Yohimbine or atipamezole (a2 antagonists)
Counteracts a2 adrenergic activity
What vehicle in amitraz is thought to contribute to its toxicity?
What medications are contraindicated with amitraz?
Other MAO inhibitors (selegiline)
TCA (amitriptyline, clomipramine)
What are the 2 classes of insect growth regulators?
Juvenile hormone analogs
Chitin synthesis inhibitors
List 3 examples of juvenile hormone analogs.
What is the MOA of juvenile hormone analogs?
JHesterase normally breaks down JH --> molting
-Mimics JH so that molting does not progress
Also causes fleas to produce infertile eggs
List 2 examples of chitin synthesis inhibitors.
What is the MOA of cyromazine?
Does not technically inhibit chitin; increases stiffness of exoskeleton so that it can't expand
What is a draw back of lufenuron as a monotherapy?
Does not kill adult fleas
Lufenuron has been proposed as a potential treatment/prevetative for what parasite?
Encephaltiozoon cuniculi in rabbits
What are the AE of lufenuron?
VD, lethargy/depression, pruritus/urticaria, dyspnea, anorexia, reddened skin
List 3 examples of neonicotinoids.
What is the MOA of neonicotinoids?
Binds nicotinic AchR on postsynaptic neuron, blocks impulses > CNS impairment death
What is the MOA specifically of dinotefuran?
Permanently binds to nicotinic AchR in the nerve synapse; Causes continuous nerve stimulation
Kills by contact; ingestion by flea is not necessary
How is nitenpyram excreted?
Unchanged in urine
What are pyrethrins? Pyrethroids?
Pyrethrins- Naturally derived volatile oil extract of the chrysanthemum flower; contact poison
Pyrethroids- synthetic, includes permethrin and deltamethrin