Antiparasitics Flashcards by Jacquie Swenson

Describe why extremely large burdens of ascarids should be treated in a cautious manner.

Ascarids are large worms and incredibly high numbers can be found infesting a single animal’s intestines. If an anthelmintic is chosen that has high efficacy against the ascarid in question, mass ascarid die-offs can cause verminous impactions in the gut.

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Select the drug that is most suitable for treating tapeworm infestations.
-Naphthalophos
-Ivermectin
-Praziquantel
-Monepantel
-Closantel
-Pyrantel

-Praziquantel

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Goat antiparasitic considerations

Goats typically metabolise the antiparasitics faster than sheep and nearly always require a higher dose

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How are antiparasitics classified?

They are S5s (“Caution”) and S6s (“Poison”)
*can get lots of them over the counter
*side step veterinary input

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Praziquantel MOA

*MOA: Not fully understood
–  Ca2+ influx into cestode
–  Ca2+ release from intracellular stores
–neuromuscular toxicity  paralysis
Very wide margin of safety

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Praziquantel clinical indications

Gold standard activity against cestodes

*In many preparations to broaden spectrum to include cestodes

*some activity against trematodes, very poor against nematodes

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What is the gold standard for treatment of cestodes?

Praziquantel

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Closantel MOA

Antitrematodals

Complex MOA causes spastic paralysis!

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Closantel clinical indications

When thinking liver fluke & Barber’s pole worm (Haemonchus contortus), think Closantel
*good activity against trematodes (flukes)
*some activity against nematodes
*good to not so good (resistance) against Haemonchus contortus

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Pharmokinetics closantel

Good oral bioavailability
-can systemically absorb and distribute to where the worms are

Extensive protein binding + long elimination half life
* 1 month DOA

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What stage of liver fluke does closantel work best aginst?

Works best against late immature stage

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Benzimidazoles “white drenches” MOA

Binds to B-tubulin, inhibiting microtubule formation  disrupting cell division and maintenance of cell shape etc
-wide safety margin

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Fenbendazole

Broad spectrum” anthelmintic (only one)
*Adult nematodes
*Trematodes (weak, except triclabendazole)
*Cestodes (weak)

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When can fenbendazole be used for small animals?

giardia

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What drug targets the early immature stage of liver flukes?

Triclabendazole

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Febantel

pyrantel & praziquantel “drontal”

-anticestodals

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Levamisole MOA

Agonist at the worm’s nicotinic ACh receptors –>sustained muscle contraction –> spastic paralysis

Potential for host toxicity – narrow safety margin (2-6x)

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Levamisole “the clear drench” clinical indications

Nematodes only

Water soluble, in water medication–> can be used for mass medication

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Tetrahydropyrimidines MOA

“pyrantel & oxantel”

Spastic paralysis in nematodes
-drugs that are closely related to levamisole (the “clear” drench)

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Tetrahydropyrimidines clinical indications

Small animal nematode infections

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Monepantel (“Zolvix”)

Par of the drug class: Amino-acetonitrile derivatives (AADs)
-new drug class
-should be combined with other drenches (to reduce anthelmintic resistance)

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Derquantel + Abamectin (“Startect”) MOA

causes flaccid paralysis

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Derquantel + Abamectin (“Startect”) clinical indications

*Excellent efficacy (>95%) against Haemonchus contortus, Trichostrongylus and Nematodirus

*Limited efficacy (<95%) against Teladorsagia (Ostertagia)
–the abamectin may not completely help with this

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Melarsomine MOA

*Arsenic based product with unknown MOA
*Low safety margin
*Complicated treatment protocols

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Melarsomine Clinical indications

Heartworm (ADULT) treatment!

What do macrocyclic lactones have no efficacy against?

Tapeworms ## Footnote Macrocyclic lactones are effective against nematodes, ticks, mites, and the L3 stage of heartworm.

List the major drug classes that target parasites.

* Anthelmintics * Ectoparasiticides * Endectocides ## Footnote These classes include various specific drugs for treating different types of parasites.

What is the mechanism of action (MOA) of benzimidazoles?

Binds to β-tubulin, inhibiting microtubule formation ## Footnote This disrupts cell division and maintenance of cell shape.

Which drug is considered the gold standard for treating cestodes?

Praziquantel ## Footnote It has good efficacy against tapeworms.

What is a common side effect of levamisole?

Potential for host toxicity ## Footnote Levamisole has a narrow safety margin (2-6x).

Fill in the blank: The main active ingredient in 'Zolvix' is _______.

Monepantel ## Footnote Monepantel is an important antinematodal for sheep.

True or False: Closantel is effective against both trematodes and nematodes.

True ## Footnote It has good activity against trematodes and some activity against nematodes.

What is the main concern regarding anthelmintic resistance?

Economic losses and welfare concerns ## Footnote Resistance continues to spread chemically, taxonomically, geographically, and clinically.

Describe the pharmacokinetics of closantel.

Good oral bioavailability, extensive protein binding, long elimination half-life ## Footnote Closantel has a duration of action of about 1 month.

Which ectoparasiticides are derived from the Chrysanthemum plant?

Pyrethrins ## Footnote Pyrethroids are synthetic derivatives that are more stable and commonly used.

Fill in the blank: The MOA of fipronil involves _______.

Spastic paralysis ## Footnote Fipronil can cause hyperactivity and convulsions in hosts.

What is the primary use of insect growth regulators (IGRs)?

Inhibit insect development ## Footnote They prevent the insect from 'growing up' and developing properly.

Select the drug that is most suitable for treating tapeworm infestations.

Praziquantel ## Footnote This is the only drug listed that has efficacy against tapeworms.

What is the main concern when treating animals with large burdens of ascarids?

Verminous impactions in the gut ## Footnote High numbers of ascarids can cause complications if an effective anthelmintic is used.

Which drug class is primarily used for treating external parasites?

Ectoparasiticides ## Footnote These include drugs for lice, fleas, ticks, and mites.

What is the main active ingredient in 'Advantage' and 'Avenge'?

Imidacloprid ## Footnote It causes insect paralysis with little binding to mammalian receptors, making it safer.

What is the active ingredient in 'Comfortis Plus'?

spinosad + milbemycin

What are the new ectoparasiticides for small animals mentioned?

Indoxacarb & Isoxazolines

What is the mechanism of action for Indoxacarb?

Neurotoxicity to fleas, metabolised into active metabolite in the flea

How long is Indoxacarb waterfast after application?

>48h after application

What are common signs of toxicity from Indoxacarb?

squinting, head shaking, salivation, scratching/rubbing

Which isoxazolines are used for ticks and fleas?

* Afoxolaner ('NexGard') * Fluralaner ('Bravecto') * Sarolaner ('Simparica') * Lotilaner * Togilaner

What is the schedule classification for Indoxacarb?

S6 POISON

What is the duration of action for Fluralaner ('Bravecto') in dogs?

1 year for fleas and paralysis ticks, 11 months for brown dog ticks

What are the most common adverse side effects of Fluralaner?

* Vomiting * Diarrhoea * Lethargy * Inappetence * Pruritis

What is the mechanism of action for Macrocyclic Lactones?

agonist at glutamate R & GABA-gated chloride ion channels, leading to flaccid paralysis

What breeds are sensitive to Macrocyclic Lactones?

* Australian Shepherds * Collies * Old English Sheepdogs * Shetland Sheepdogs * Border Collies

What is the toxicity of Macrocyclic Lactones primarily due to?

inadvertent GABA agonism in the host

Which drug is safe for use in Collie breeds?

Moxidectin ('Proheart')

Fill in the blank: The insect growth regulators act by inhibiting insect growth hormone or _______.

chitin synthesis

True or False: The pyrethroids are most toxic to dogs.

False

What is a unique characteristic of the new sheep drugs regarding wool WHP?

Wool rehandling period and wool harvesting interval are now split

What is the active ingredient in 'Revolution Plus' for cats?

Sarolaner + Selamectin

What is the duration of action for 'Credelio Plus'?

monthly chewable

Which Macrocyclic Lactone is known as 'Ivomec'?

Ivermectin

What type of lice do pour-on Macrocyclic Lactones kill?

* Biting lice (epidermal feeders) * Sucking lice (blood feeders)

What is the recommended route of administration for Ivermectin in sheep?

oral drench, pour-on, injectable

Fill in the blank: The organophosphates and macrocyclic lactones can kill _______ and ecto-parasites.

endo-parasites

What is one of the broadest antiparasitic spectrums on the market?

Imidacloprid, Moxidectin ('Advocate')

What is the main side effect concern when using Macrocyclic Lactones?

host ataxia, sedation

What is the active ingredient in 'NexGard Spectra' for dogs?

Afoxolaner + Milbemycin

True or False: Isoxazolines are effective without a blood meal.

False

What is the purpose of the Dimethylacetamide solvent in Fluralaner?

facilitates percutaneous absorption

What type of parasites do macrocyclic lactones primarily target?

Nematodes and ectoparasites ## Footnote Macrocyclic lactones include drugs like Ivermectin and Abamectin.

What is the mechanism of action of organophosphates?

AChE inhibitors leading to increased ACh at nicotinic receptors and spastic paralysis ## Footnote Organophosphates are known for their potential toxicity to hosts.

What are the common signs of muscarinic toxicity from organophosphates?

Salivation, lacrimation, urination, defecation (SLUD), bradycardia, miosis ## Footnote These signs indicate overstimulation of muscarinic receptors.

What are the common signs of nicotinic toxicity from organophosphates?

Muscle tremors, twitching, seizures ## Footnote Nicotinic toxicity results from overstimulation at nicotinic receptors.

What is Fluazuron classified as?

Chitin synthesis inhibiting insect growth regulator (IGR) ## Footnote Fluazuron is used to control tick populations among other parasites.

What are the active ingredients in 'Equimax liquid allwormer'?

Avermectin and praziquantel ## Footnote It is used for antinematodal and anticestodal activity.

What is the formulation of 'Eraquell Pellets'?

Ivermectin ## Footnote It is an avermectin used for antinematodal and boticidal activity.

What does 'Equest Plus Tape' contain?

Moxidectin and praziquantel ## Footnote It is effective for antinematodal, boticidal, and anticestodal activity.

What is the spectrum of activity expected from a topical preparation of imidacloprid and moxidectin in a dog?

Treatment of fleas, mites (including demodex), and intestinal nematodes; prevention of heartworm ## Footnote This combination targets multiple parasites effectively.

True or False: Macrocyclic lactones are effective against tapeworms.

False ## Footnote The macrocyclic lactones do not have efficacy against tapeworms.

What are the three classifications of parasite chemotherapy?

Endoparasiticides, ectoparasiticides, endectocides ## Footnote These classifications help in understanding the treatment spectrum.

What is a common application method for organophosphates?

Topical preparations such as collars and sprays ## Footnote These methods minimize systemic absorption.

Fill in the blank: The 'NAPfix' formulation includes naphthalophos, _____, and abamectin.

Albendazole ## Footnote 'NAPfix' is used to address resistance in parasite management.

What is the effect of organophosphate flea collars?

Disperses fine powder over the body when the animal moves ## Footnote Care should be taken to prevent ingestion.

What is the potential duration for withholding periods (WHP) when using organophosphates?

Very short (0 days) to very long (several weeks) depending on the specific OP used ## Footnote This variability affects treatment planning.

Antiparasitics Flashcards

(84 cards)