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General Pharmacology 2 > Anthelmintic drugs > Flashcards

Anthelmintic drugs Flashcards

1
Q

Benzimidazoles and probenzimidazoles

A
  • Drugs include:
    • albendazole, fenbendazole, oxfendazole
  • Pro-BZD:
    • inactive prodrugs: febantel
  • Indications:
    • several groups of nematodes, Moniezia
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2
Q

Benzimidazoles and probenzimidazoles

Pharmacodynamics

A

MOA: Inhibition of microtubule polymerization

  • Binding to parasite B-tubulin, which produces subsequent disruption to the tubulin- microtubule dynamic equilibrium
  • Alteration of cell division, maintencance of cell shape, cell motility, cell secretion, nutrient absorption, and intracellular transport
  • Dissociation rate of BZD form parasite tubulin is much lower than mammalian tubuline

Oral ONLY

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3
Q

Benzimidazoles and probenzimidazoles

Pharmacokinetics in ruminants

A
  • single oral dose, has systemic distribution
  • Limited water solubility - affects absorption
  • Effect of reduced GI transit time: increased absorption
  • Effect on the type of diet:
    • binding to fibers produced in “rumen reservoir”
  • Liver damage:
    • decreased rate of BZD biotransformation and delayed elimination
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4
Q

Benzimidazoles and probenzimidazoles

Pharmacokinetics of non-ruminant species

A
  • Horses:
    • oral - reduced bioavailability and shorter residence times
  • Cats, dogs, and man:
    • oral - only limited rates of dissolution and absorption
      • BZ may need to be given at a higher dose or as multiple administrations in order to maintain therapeutic concentrations
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5
Q

Benzimidazoles and probenzimidazoles

Safety / toxicity

A
  • One of the least toxic of the available anthelmintics
  • BZs do not affect microtubule synthesis in animal cells
  • Fenbedazole:
    • rare vomiting and diarrhea Pancytopenia
  • Albendazole:
    • teratogenic and embryotoxic in pregnant animals
  • BZDs may be toxic to liver and bone marrow in dogs, particularly high doses
  • Not recommended for cats
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6
Q

Benzimidazoles and probenzimidazoles

usage:

Albendazole

A
  • Cattle
    • liver flukes, tapeworms, GI worms, lung worms
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7
Q

Benzimidazoles and probenzimidazoles

usage

Fenbendazole

A
  • Cattle:
    • GI worms, lungworms tapeworms of L4 ostertagia
  • Horses:
    • strongyles, pimworms, ascarids
  • Goats:
    • GI worms, lungworms
  • Dogs:
    • Giardia, roundworms, hookworms, whipworms
  • Cats:
    • not currently approved for use in domestic cats, but approved for large zoo felines
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8
Q

Benzimidazoles and probenzimidazoles

usage

Oxfendazole

A

Cattle: Beef and non-lactating dairy

Lungworms, GI nematodes, tapeworms

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9
Q

Nicotinic Agonists - levamisole

A

Drug class: imidazothiazoles

Indications: Several groups of nematodes

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10
Q

Nicotinic Agonists - levamisole

Pharmacodynamics

A

MOA: Nicotinic agonsit

  • Levamisole is a cholinergic receptor agonist
  • Prolonged activation of the excitatory nicotinic acetylcholine receptors on nematode body wall muscle
  • Elicits spastic muslce paralysis and prevents egg laying
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11
Q

Nicotinic Agonists - levamisole

Pharmacokinetics

A

Oral - absorbed in gut and distributed systemically

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12
Q

Nicotinic Agonists - levamisole

Safetly / toxicity

A
  • Low margin of safety; can act on mammalian nAChR
  • Both muscarinic and nicotinic effects
  • Salivation, defecation, respiratory distress from smooth muscle contration, death
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13
Q

Nicotinic Agonists - levamisole

Usage

Immunomodulatory effects: ruminants

A

2-3 mg/kg body weight

Improves function of T cells and phagocytes, but not B cells

Activity is sometimes unpredicatable

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14
Q

Nicotinic Agonsits - Pyrantel, Morantel

A

Drug Class: Tetrahydropyrimidines

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15
Q

Nicotinic Agonsits - Pyrantel, Morantel

Pharmacodynamics

A

MOA: nicotinic agonist

  • Act selectively as agonists at synaptic and extra-synaptic nicotinic Acetlycholin receptors (nAChR) on nematode muscle cells
  • Produce contraction and spastic paralysis
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16
Q

Nicotinic Agonsits - Pyrantel, Morantel

Pharmacokinetics

A

Pyrantel tartrate: well absorbed after oral administration in most species but not in ruminants

Pyrantel pamoate: poorly absorbed form the GI tract

Morantel: Negligibly absorbed in ruminants

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17
Q

Nicotinic Agonsits - Pyrantel, Morantel

Safety and Toxicity

A
  • Pyrantel activates mammalian AChRs with low efficacy
  • Salts of pyrantel
    • no toxic effects in all animal hosts up to 7x therapeutic dose
  • Pyrantel tertrate is slightly less tolerated in horses than pamoate salt
  • Pyrantel is not recommended in severely debilitated animals
  • Withdrawal periods exist for swine and ruminants
  • Avoid combining piperazine and pyrantel/morantel
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18
Q

Nicotinic Agonsits - Pyrantel, Morantel

Usage of Pyrantel

A
  • Horses:
    • both salts available
  • Dogs
    • pamoate
    • give with food - delays GI transit time, longer action on GI parasites
  • Swine:
    • tartrate salt in ration
  • Morantel tartrate
    • ruminants
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19
Q

Macrocyclic lactones

A

Two major groups:

Avermectins: Ivermectin, selamectin, eprinomectin, doramectin

Milbemycins: milbemycin oxime, and moxidectin

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20
Q

Macrocyclic lactones:

Pharmacodynamics

A

MOA: ligand gated chloride channel agonists

  • MLs bind to GABA and or GLutamate-gated chloride challens with high affinity
  • Increases chloride conductance across cell membranes
  • Induce reduction in motor activiry and paralysis in both arthropods and nematodes
    • pharyngeal muscles paralysed - interferes with feeding
    • Flaccid paralysis - inhibits body movements
    • Paralysis of ovijector - inhibits egg laying and reproduction
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21
Q

Macrocyclic Lactones

Pharmacokinetics

A

injectable: long plasma half life in cattle, long persistency in tissues, long withdrawal periods

22
Q

Macrocyclic Lactones:

Safety / toxicity

A

MLs are generally safe, except in MDR -/- dogs

Acute toxic signs include CNS depression, ataxia, and possible death

23
Q

Emodepside

A

Drug class: cyclo-octadepsipeptide

24
Q

Emodepside:

Pharmacodynamics

A

MOA: latrophilin receptor agonist

  • Acts presynaptically on a latrophilin-like receptor of nematodes → inhibitory neuropeptide release → paralysis
  • Also may activate calcium dependent potassium channels → K+ influx → Paralysis
  • Product:
    • topical - cats - against nematodes
25
Q

Emodepside:

Pharmacokinetics

A

topical application

rapidly absorbed transdermally

26
Q

Emodepside:

Safety / toxicity

A

if orally administered: salivation, vomiting, and mild neurologic effects

27
Q

Emopdepside:

Usage

A

Cats: ascarids, hookworms

NO DOG products in the US

Oral administration of cat topical product to dogs for MDR A. caninum is OFF-label

28
Q

Piperazine

A

Drug class: heterocyclic compounds

Marrow-spectrum antinematodal

29
Q

Piperazine:

Pharmacodynamics

A

MOA: GABA receptor agonist

  • Selective agonist of y-amino butyric acid receptors → opening of chloride channels → hyperpolarization of the membrane of the muscle cells of the menatode → flaccid paralysis → removal
  • Was previously available for swine, but not currently
30
Q

Piperazine:

Pharmacokinetics

A

readily absorbed througn the GI tract and then extensively metabolized

31
Q

Piperazine:

Safety / toxicity

A

Almost nontoxic under ordinary circumstances

Large safety margin

Do NOT comine with pyrantel

32
Q

Piperazine:

Usage

A

yound dogs for toxocara canis

33
Q

Melarsomine

A

Drug class: arsenical

Product: injectable

34
Q

Melarsomine:

Pharmacodynamics

A

MOA: not well understood

  • arsenic interactions with sulfhydryl groups within cells
  • Binding of trivalent arsenic to sulfhydryl groups of proteins or enzymes can disrupt aerobic metabolism in kidneys, liver, and GI tract
35
Q

Melarsomine:

Pharmacokinetics

A

rapidly absorbed after IM injection

Acheiving the Cmax at only 8 min post injection

Arsenic plasma levels are higher and measured of a longer time after treatment

36
Q

Melarsomine:

Safety / toxicity

A

Overdose: can occur if mg/lb is used instead of mg/kg

Excessive salivation, panting, restlessness, and fever, vomiting, and diarrhea

3x therapeutic dose = death

Dimercaprol is reported in the literature to be an antidote for arsenic toxicity

37
Q

Diethylcarbamazine Citrate

A

derivative of piperazine

Used in MDA for lymphatic filariasis along with ivermectin and albendazole in humans

Historically used for D. immitis

Was a microfilaricide, but would induce shock-like symptoms sometimes

38
Q

Monepantel

A

Drug class: aminoacetonitrile derivatives

Not available in the US

Sheep formulation

Resistance within 5 years of introduction in Austrailia/NZ

39
Q

Proziquantel

A

Drug class: isoquinolinepyrazine

Activity against adults and larval stages of cestodes and trematodes

40
Q

Proziquantel:

Pharmacodynamics

A

MOA: Ca2+ channel agonist

  • Not completely known, thought to act on voltage gated Ca2+ channels
  • Induces a rapid and sustained paralytic muscle contraction
  • Induces tegumental disruption
  • Metabolic changes - decrease in glucose uptake, glycogen storage, ATP content, and lactate release
  • Products:
    • oral or injectable
41
Q

Praziquantel:

Pharmacokinetics

A

Completely absorbed in the GI tract in most species

Low oral bioavailability in sheep

42
Q

Praziquantel

Safety / toxicity

A

overdoses of up to 5x are tolerated without adverse effects

43
Q

Praziquantel

Usage

A

dogs and cats: cestodes

Horses, anoplocephala

44
Q

Epsiprantel

A

Similar to praziquantel

45
Q

Epsiprantel:

Pharmacodynamics

A

MOA: Ca2+ channel agonist

affects Ca2+ homeostasis within the parasite

damages the tegument

46
Q

Epsiprantel:

Pharmacokinetics

A

orally: poorly absorbed in the GI tract

47
Q

Epsiprantel;

Safety / toxicity

A

prolonged treatments: emesis

48
Q

Epsiprantel:

Usage

A

cats and dogs

49
Q

Clorsulon

A

Drug class: Benzenesulfonamide

Adult liver flukes in cattle

50
Q

Clorsulon:

Pharamcodynamics

A

MOA: metabolic enzyme inhibitor

Competitively inhibit fluke metabolic enzymes

51
Q

Clorsulon:

Safety / toxicity

A

Safe drug with hig therapeutic index

Considered safe for use in breeding and pregnant animals

52
Q

Clorsulon:

Usage

A

cattle: liver flukes

General Pharmacology 2 (17 decks)

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