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Module 16 > Anthelmintics: Factors Influencing Use in Companion Animals > Flashcards

Anthelmintics: Factors Influencing Use in Companion Animals Flashcards

1
Q

what are group 1 anthelmintics

A

Group 1: benzimidazoles (BZ, white drenches)

Fenbendazole (Febantel UK, Panacur, Safe Guard)

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2
Q

what are group 2 anthelmintics

A

Group 2: levamisoles (LV, yellow drenches)

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3
Q

what are group 3 anthelmintics

A

Group 3: macrocyclic lactones (ML, clear drenches)

Ivermectin (Heartgard, Ivomec, Eqvalan, Bimectin)

Moxidectin (Coraxis, Cydectin, ProHeart, Advantage, Multi Bravecto Plus, Simparica Trio, Quest - horses)

Milbemycin oxide (in combo products with lufenuron Sentinel)

Selamectin (Revolution, Paradyne)

Eprinomectin (Eprinex, LongRange, Eprizero, Centragard combo with praziquantel)

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4
Q

what are group 4 anthelmintics

A

Group 4: amino acetonitrile derivatives (AD, orange drenches)

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5
Q

what are group 5 anthelmintics

A

Group 5: multi-actives

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6
Q

what are examples of praziquantel

A

Droncit, Drontal, Drontal Plus

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7
Q

what are examples of benzimidazoles

A

panacur (fenbendazole)

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8
Q

what is the primary action of benzimidazoles

A

binds helminths tubulin and prevents microtubules formation

tubules absent 6-24 hours

starves parasite

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9
Q

what are other mechanisms benzimidazoles

A

inhibition of mitochondrial fumarate reductase

reduced glucose transport

uncoupling of oxidative phosphorylation

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10
Q

what is the administration of benzimidazoles

A

oral administration of suspension

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11
Q

how is benzimidazole absorbed

A

limited from gut, most leave the dog in feces

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12
Q

how is benzimidazole distributed

A

plasma levels typically <1% of oral dose

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13
Q

how is efficacy of benzimidazole improved

A

if gut transit time slowed

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14
Q

how long is benzimidazole present

A

totally eliminated in 48 hours

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15
Q

what is the metabolism of benzimidazole (3)

A

variable

  1. reduction (sulphoxide –> sulphide)
  2. oxidation (sulphide –> sulphoxide –> sulphone)
  3. cyclization (ruminants only: netobimin –> albendazole)

sulphides and sulphoxides – ACTIVE

sulphones – INACTIVE

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16
Q

what are examples of macrocyclic lactones

A

milbemax (milbemycin oxime), stronghold (selamectin) – cats and dogs

animec, bimectin, eqvalan, eraquell (all ivermectin) – horses

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17
Q

what is the spectrum of macrocyclic lactones

A

stimulate glutamate gated chloride channels in invertebrate nerve and muscles

chloride influx causes hyperpolarization of the post synaptic cells

interferes with neurotransmission

results in flaccid paralysis –> GABA activity may be involved at higher concentrations

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18
Q

what type of compound are macrocyclic lactones

A

large lipophilic compounds

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19
Q

how long do macrocyclic lactones

A

generally persistent

long half-life

long period of efficacy

20
Q

where are macrocyclic lactones distributed

A

accumulation in fat

21
Q

how are macrocyclic lactones excreted

A

bile, urine

but >90% feces

22
Q

what are the main factors that affect macrocyclic lactone absorption (3)

A
  1. route of administration
  2. formulation
  3. animal species
23
Q

what is ivermectin a mix of

A

two compounds

22,23-dihydroavermectin B1a (80%) and B1b (20%)

24
Q

what is the half life of ivermectin

A

approx 3 days for oral

2 days for IV

spot on 10-11 days

25
Q

how is ivermectin excreted

A

fecal excretion

26
Q

why is ivermectin toxic to colies, aussies etc

A

MDR1 encodes for P glycoprotein pump which prevents ivermectin from entering the brain through the blood brain barrier

if there is an MDR1 mutation then there is no production of the p glycoprotein pump

27
Q

what is selamectin

A

modified avermectin

revolution

28
Q

what is the half life of selamectin

A

11 days

29
Q

what is the safety of selamectin

A

little or no adverse reaction reported

30
Q

what are the formulations of mibemycin oxime

A

chewable tablet for cats and dogs

31
Q

what are the pharmacokinetics of mibemycin oxime

A

90-95% remains in GIT

32
Q

what is the safety of mibemycin oxime

A

transient trembling/ataxia

33
Q

what is the mechanism of action of tetrahydropyrimidines

A

stimulate nicotinic acetylcholine receptors (depolarizing neuromuscular blocking agents)

higher affinity for parasite receptor

paralyzes worm

34
Q

what are examples of tetrahydropyrimidines

A

embotape, pyratape (pyrantel) – horses

dronal, ednogard (pyrantel combo) – dogs and cats

35
Q

how are tetrahydropyrimidines absorbed

A

not well absorbed from GIT

36
Q

how are tetrahydropyrimidines excreted

A

50% excreted unchanged remainder in feces

37
Q

what are tetrahydropyrimidines effective against

A

very effective against GIT luminal parasites

38
Q

how is the tissue penetration of tetrahydropyrimidines

A

poor

39
Q

what is the mechanism of action of praziquantel

A

tetanic contraction of parasite musculature

rapid vacuolization of the syncytial tegument

40
Q

what are the safety issues with praziquantel

A

high therapeutic index

41
Q

what is the spectrum of activity of praziquantel

A

cestodes, trematodes

efficacy vs. larval cestodes very variable

42
Q

how is praziquantel absorbed

A

rapidly absorbed, widely distributed

43
Q

how is praziquantel metabolized

A

70% first pass metabolism

80% eliminated within 24 hours

44
Q

what is the mechanism of action of cyclooctadepsipeptides

A

inhibition of acetylcholine-elicited muscle contraction

pre-synaptic action (iatrophilin like receptor)

ultimately flaccid paralysis/death

45
Q

what is the spectrum of activity of cyclooctadepsipeptides

A

adult nematodes

46
Q

what is the pharmacokinetics cyclooctadepsipeptides

A

extensively distributed

high Vd

minor metabolism

excreted unchanged in the bile

Module 16 (26 decks)

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