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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
Q

Spinosad:

Safety / toxicity

A

Adverse reactions are rare; vomiting possible

Drug-Drug interactions between spinosad and ivermectin

26
Q

Spinosad:

Usage

A

Dogs and cats: fleas

27
Q

Isoxazolines

A

Afloxalaner, Fluralaner, Sarolaner, Lotilaner

28
Q

Isoxazolines:

Pharamcodynamics

A

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
Q

Isoxazoline:

Pharmacokinetics

A

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
Q

Isoxazolines

safety / toxicity

A

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
Q

IsoxazolinesL

Usage

A

Fleas and ticks

combination products are available

32
Q

Macrocyclic lactones

A

endecticides

avermectins

milbemycins

33
Q

Macrocyclic lactones:

phamacodynamics

A

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
Q

Macrocyclic lactones:

usage

A

cattle: pour-on, injection

lice, mites, hypoderma, horn flies

35
Q

Sythetic pyrethroids

A

Permethrin, deltamethrin, flumethrin, fenvalerate, cypermethrin, phenothrin

Drug class: pyrethroids

36
Q

Synthetic Pyrethroids

Pharmacodynamics

A

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
Q

Synthetic Pyrethroids

Pharmacokinetics

A

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
Q

Synthetic pyrethroids

Safety / toxicitiy

A

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
Q

Synthetic pyrethroids

Usage

A

Dogs and cats: shampoos, spot-on, collar

Cattle: dusts, pour-on, eartags,

Horses: sprays

Environmental control

40
Q

Organophosphates

A

dichlorvos, coumaphos

41
Q

Organophosphates

Pharmacodynamics

A

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
Q

Organophosphates

Products

A

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
Q

Organophosphates

Pharmacokinetics

A

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
Q

Organophosphates

Safety / toxicity

A

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
Q

Amitraz

A

Drug class: formamidine

46
Q

Amitraz:

pharmacodynamics

A

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
Q

Amitraz

pharmacokinetics

A

Not well understood

48
Q

Amitraz

Safety / toxicity

A

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
Q

Amitraz:

Usage

A

Dogs: spot-on, concentrate liquid, collar

Cattle, swine: Concentrate liquid

50
Q

Repellents

A

butoxypolypropylene glycol (stabilene), di-n-propyl isocinchomeronate (MGK 326), and diethyl-m-toluamide (DEET)

51
Q

Repellents

Pharmacodynamics

A

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
Q

Repellents:

Usage

DEET

A

Approved by US EPA for use in dwellings, on the human body and clothing, and pet living/sleeping quarters

53
Q

Repellents

usage

MGK 326

A

often formulated with pyrethroids and or synergist to be used as sprays, dips, and shampoos in horses, dogs, and cats

54
Q

Repellents

usage

Butoxypolypropylene glycol

A

formulated with a pyrethroid insecticide

General Pharmacology 2 (17 decks)

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