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General Pharmacology 2 > Ectoparasiticides > Flashcards

Ectoparasiticides Flashcards

1
Q

Fipronil

A

Drug class: phenylpyrazole

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2
Q

Fipronil:

pharmacodynamics

A

MOA: GABA receptor antagonist

  • Binds to the y-aminobutryric acid receptors of insects
  • inhibits the influx of Cl- ions into the nerve cell
  • Resulting in hyperexcitability of the insect nervous system
  • May also bind to and block glutamate-activated chloride channels
  • In mammals, fipronil binding ot the GABA receptor is less effective → accounts for its wide margin of safety
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3
Q

Fipronil:

Pharmacokinetics

A

topical application: translocation of the chemical over the entire body with significant deposition in sebum, sebaceous glands, and hair follicles

Minimal systemic absorption

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4
Q

Fipronil:

safety

A

wide margin of safety

extralabel use in young or small rabbits can cause seizures and death

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5
Q

Fipronil:

Usage

A

Dogs and Cats: topical - fleas, ticks, chewing lice

Available in combination with IGRs to kill juvenile stages of fleas

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6
Q

Insect Growth Regulators (IGRs)

A

juvenile-hormone analogs and insect development inhibitors

Harmless to the pet, livestock, and humans

Affect the developing stages of arthropods but not the adult ectoparasites

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7
Q

Juvenile-hormone analogs

A

methoprene, pyriproxifen

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8
Q

Juvenile-hormone analogs

Pharmacodynamics

A

MOA: mimic insect juvenile hormones

  • In the normally developing insect, the hormone levels usually decrease prior to the adult stage
  • Falsely signal arthropod to remain in its immature egg or larval stage and not develop to adult stage
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9
Q

Juvenile-hormone analogs

usage

A

available in combination with several groups of ectoparasiticides

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10
Q

Insect development inhibitors

A

Diflubenzuron, iufenuron

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11
Q

Insect development inhibitors

Pharamcodynamics

A

MOA: chitin synthesis inhibitors

  • Interfere with the development of the insect exoskeleton by inhibiting chitn synthesis or deposition pathways
  • Chitin is an essential constituent of flea eggshells and exoskeleton of immature fleas
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12
Q

Insect development Inhibitors:

usage

A

Diflubenzuron: feed-through fly control

Lufenuron: ingested by adult flea, is deposited in egg and prevents hatching

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13
Q

Imidacloprid, Dinotefuran, Nitenpyram

A

Drug class: neonicotinoids

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14
Q

Imidacloprid, Dinotefuran, Nitenpyram

Pharmacodynamics

A

MOA: Ach receptor agonist

  • Modeled after natural nicotine and are acetylcholine mimics
  • Binding irreversibly to postynaptic nicotinic acetylcholine receptors in insects causing the post-synaptic Na+ channels to remain continuously open
  • Causes overstimulation of the nervous system, producing spontaneous muscular contractions followed by hyper-depolarization leading to paralysis and death
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15
Q

Imidacloprid, Dinotefuran

pharmacokinetics

A

Topical - no significant dermal absorption into blood → surface translocation → whole-body coverage

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16
Q

Imidacloprid, Dinotefuran

safety / toxicity

A

Imidacloprid: Typically safe

Dinotefuran: skin irritation

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17
Q

Imidacloprid, Dinotefuran

Usage of imidacloprid

A

spot on, collar: control fleas in dogs and cats

Combined with permethrin, flumethrin, pyriproxyfen, moxidectin

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18
Q

Imidacloprid, Dinotefuran

usage of dinotefuran

A

Spot on: efficacy against fleas

Dog formulation has permethrin

Do not use combination product in cats

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19
Q

Nitenpyram

Pharmacokinetics

A

Readily absorbed int he GI tract

Fleas begin falling off the coat of dogs and cats within 30 minutes

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20
Q

Nitenpyram

Saftey / toxicity

A

very safe

Transient itching period observed within 1-2 hours after treatment

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21
Q

Nitenpyram

Usage

A

dogs and cats, can be used daily

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22
Q

Spinosad

A

Drug class: spinosyn

23
Q

Spinosad:

pharmacodynamics

A

MOA: Ach receptor agonist

  • Binds to nicotinic acetylcholine receptors on post synaptic membranes of the insect nervous system
  • But these are distinct form receptors affected by other neonicotinoids
  • Limits the possibilitiy for cross-resistance with similar related insecticides
  • Kills insects via hyperexcitation of the insect nervous system
24
Q

Spinosad:

Pharmacokinetics

A

Oral: quickly absorbed to blood

starts to kill fleas within 30 minutes of admin

Better bioavailability when administered with food

25
Spinosad: Safety / toxicity
Adverse reactions are rare; vomiting possible Drug-Drug interactions between spinosad and ivermectin
26
Spinosad: Usage
Dogs and cats: fleas
27
Isoxazolines
Afloxalaner, Fluralaner, Sarolaner, Lotilaner
28
Isoxazolines: Pharamcodynamics
MOA: GABA receptor antagonist * non-competitve GABA receptor antagonist * Much more selective for GABA receptors in insects or ticks, than for those in mammals * Bind to Cl- channels and block influx of Cl- * Resulting in initial hyperexcitability of the insect nervous system, then paralysis and death
29
Isoxazoline: Pharmacokinetics
High oral bioavailability, widely distributed in body Half-life is long in dogs Fleas exposed following attachement and feeding - onset of effect can occur within 8 hours of attachment For ticks: onset of death is within 48 hours of attachment
30
Isoxazolines safety / toxicity
safe. very selective for fleas and tick nervous system compared to mammalian nervous system Adverse effects: rare thus far. although vomiting, diarrhea, lethargy, and anorexia have been observed
31
IsoxazolinesL Usage
Fleas and ticks combination products are available
32
Macrocyclic lactones
endecticides avermectins milbemycins
33
Macrocyclic lactones: phamacodynamics
MOA: ligand gated chloride channel agonists * MLs bidn to GABA and/or glutamate-gated chloride channels with high affinity * Very selective for the glutamate-gated channels in nematodes and arthropods, but which are lacking in mammals
34
Macrocyclic lactones: usage
cattle: pour-on, injection lice, mites, hypoderma, horn flies
35
Sythetic pyrethroids
Permethrin, deltamethrin, flumethrin, fenvalerate, cypermethrin, phenothrin Drug class: pyrethroids
36
Synthetic Pyrethroids Pharmacodynamics
MOA: Na+ channel agonist * Interaction with the pyrethroid with the sodium channel causes the channel to remain open in insect nerves * Leads to a slowing of both the activation and inactivation process → causes the now modified channel to be in a stable hyperexcitable state * Repetivie discharges or membrane depolarization and ultimately death ofthe ectoparasite * Extremely selective for insects over mammals * Insect sodium channels can be as much as 100 times more sensitive than mammalian brian channels
37
Synthetic Pyrethroids Pharmacokinetics
Dermal abosrption is very limited; reside in the outermost layer of the skin with littel or no penetration into the systemic circulation More resistant to breakdown, greater residual activity
38
Synthetic pyrethroids Safety / toxicitiy
Cats are more sensitive than dogs to pyrethroids - can cause neurological effects and death Aquatic animals such as fish and invertebrates are highly susceptible to pyrethroids
39
Synthetic pyrethroids Usage
Dogs and cats: shampoos, spot-on, collar Cattle: dusts, pour-on, eartags, Horses: sprays Environmental control
40
Organophosphates
dichlorvos, coumaphos
41
Organophosphates Pharmacodynamics
MOA: AchE inhibitor * Irreversibly inhibit acetylcholinesterase by phosphorylation * Inhibition of AChE results in accumulation of acetylcholine to cholinergic receptors * repeated depolarization lead to paralysis and death to the parasite
42
Organophosphates Products
becoming less popular for use in and around domestic animals persistence in the environment - negatively influence the ecosystem Old OPs approved by US EPA for use in companion or food animals species are no longer marketed or available for veterinary use
43
Organophosphates Pharmacokinetics
Topical: systemic bioavailability following topical application is limited, but these are distributed across the entire coat of the animal by lateral diffusion following topical applicaiton to a localized region
44
Organophosphates Safety / toxicity
Inhibition of AChE can result in muscarinic and nicotinic effects Other drugs may potentiate the toxicity of OPs: phenothiazine tranquilizers, aminoglycodise antibiotics, and neuromuscular blocking agents such as levamisole and nicotine
45
Amitraz
Drug class: formamidine
46
Amitraz: pharmacodynamics
MOA: octopamine receptor agonist * Activates a- and B- adrenergic like octopamine receptors * Inhibits neurotransmission resulting in flaccid paralysis * Inhibits monamine oxidase that normally metabolize neurotransmitter amines present in the CNS * No effect on cholinesterase activity
47
Amitraz pharmacokinetics
Not well understood
48
Amitraz Safety / toxicity
toxic to cats and horses 5-10 times label dose causes toxicity in dogs Accidental consumption of amitraz flea collars by dogs has resulted in toxicosis
49
Amitraz: Usage
Dogs: spot-on, concentrate liquid, collar Cattle, swine: Concentrate liquid
50
Repellents
butoxypolypropylene glycol (stabilene), di-n-propyl isocinchomeronate (MGK 326), and diethyl-m-toluamide (DEET)
51
Repellents Pharmacodynamics
MOA: * Preventing the entry or landing of insect on hair coat, interfere with or inhibit feeding, causing disorientation * Some repellents can be ectoparasiticidal most repellents are not ectoparasiticidal * They prevent transmission of vector-borne diseases
52
Repellents: Usage DEET
Approved by US EPA for use in dwellings, on the human body and clothing, and pet living/sleeping quarters
53
Repellents usage MGK 326
often formulated with pyrethroids and or synergist to be used as sprays, dips, and shampoos in horses, dogs, and cats
54
Repellents usage Butoxypolypropylene glycol
formulated with a pyrethroid insecticide

General Pharmacology 2 (17 decks)

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