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Pharmacology II > LEC 23 - Anti-Nematodals > Flashcards

LEC 23 - Anti-Nematodals Flashcards

1
Q

How are definitive hosts most commonly infected with nematodes?

A

Consumption or via vector (ie. biting)

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2
Q

Why is it so hard to treat nematodes?

A

They are very intimately related with the GI tract and therefore making it hard to get to the worm.

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3
Q

What are the five types of anti-nematodals?

A 
Benazmidazoles 
Imidathiazoles
Tetrahydropyrimidines 
Piperazines 
Arsenicals
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4
Q

What are the two types of benzamidazoles?

A

Albendazoles and fenbendazole

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5
Q

What are the two types of imidathiazoles?

A

Levamisole and Tetramisole

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6
Q

What are the three types of tetrahydropyrimidines?

A

Pyrantel pamoate, Pyrantel tartrate, and Morantel tartrate

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7
Q

What are the two types of piperazines?

A

Piperazine and diethylcarbamazine

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8
Q

What drug is considered an arsenical?

A

Melarsomine

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9
Q

How do benzimidoles work?

A

Inihibit microtubule polymerization by binding B-tubulin in all worm stages. Binding is reversible. Also there is a toxic effect on the parasites. Worms will DIE prior to elimination

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10
Q

How does benzimidoles cause a toxic effect on worms?

A

GI secretory defects, will reduce glucose uptake by the worm GI tract

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11
Q

How well are benximidoles absorbed?

A

Water insoluble compounds. Formulated as pastes, suspensions and pellets.

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12
Q

How do you increase the efficacy of benzimiadoles?

A

Increased time in the GI tract.

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13
Q

What are the absorption characteristics of benzimiadoles in ruminants?

A

Rumen is a reservoir. Mixing increases the time the drug spends in the rumen. Acid pH of abomasum solubilizes the drug and increases its solubility.

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14
Q

What is the dosing regime in cattle for benzimiadoles?

A

One dose followed by a possible second dose 4 to 6 weeks later

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15
Q

What are the absorption characteristics of benzimiadoles in monogastrics?

A

Absorption decreased due to quick time in GI Tract. Acid pH of stomach does help solubilize the drug somewhat.

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16
Q

What is the dosing regime in monogastrics for benzimiazoles?

A

Once every 24 hours for 3 days minimum (depends on the organism that is present)

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17
Q

How are benzamidazoles metabolized?

A

Liver. Which produces active metabolites.

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18
Q

What are the side effects of benzamidazole?

A

Hypersensitivity reactions to antigens from dying worms

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19
Q

Fenbendazole indications: Dogs

A

Roundworms, hookworms, whipworms, and tapeworms

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20
Q

Fenbendazole indications: Cats

A

Roundworms, hookworms, strongyloides, lung worms, and giardia

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21
Q

Fenbendazole indications: Cows

A

Lung worms, stomach worms, intestinal worms, Haemonchus

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22
Q

Fenbendazole indications: Horses

A

Strongyles, pinworms, and ascarids

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23
Q

What is a side effect of fenbendazole?

A

Pancytopenia

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24
Q

What is febantel?

A

Pro-fendendazole that is metabolized to fenbendazole following absorption

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25
Q

What animals is febantel used in?

A

Dogs and cats

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26
Q

What is within drontal plus?

A

Febental, pyrantel pamoate, and praziquantel

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27
Q

Indications for Albendazole: Cats and dogs

A

Giardia only

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28
Q

Indications for Albendazole: Cows

A

Liver flukes, stomach worms, intestinal worms, and lung worms

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29
Q

What is albendazole approved for used in besides cats, dogs, and cattle?

A

Sheep, goats, and rodents

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30
Q

What are the side effects of albendazole?

A

Aplastic anemia in dogs, cats, and possible humans. Potentially teratogenic

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31
Q

Because of albendazoles teratogenic effects what should be given instead?

A

Fenbendazole in pregnant animals

32
Q

What are the two forms of dl-tetramisole?

A

l-tetramisole and d-tetramisole

33
Q

What are the characteristics of l-tetramisole?

A

Anti-nematodal effects, but also has toxicity

34
Q

What are the characteristics of d-tetramisole?

A

No anti-nematodal effects as well has having toxicity.

35
Q

What is another name for l-tetramisole?

A

Levamisole

36
Q

What is the mechanism by which Levamisole works?

A

Nicotinic receptor agonist. Stimulation of nicotinic receptors in worm muscles cause tetanic paralysis.

37
Q

how are the worms rid of with the use of levamisole?

A

Come out in feces, alive

38
Q

What animals is the use of levamisole not indicated in?

A

Horses, dogs, and cats

39
Q

indications for the use of levamisole in cattle, sheep and goats?

A

Mature/larval lung worms, mature stages of GI worms

40
Q

Indications for the use of levamisole in swine?

A

Mature stages of GI worms

41
Q

How is imdiothiozoles administered? Which is preferred?

A

PO, Topical, or SC. Oral is preferred because of the destruction of meat.

42
Q

What is the ranking of BA when it comes to the route of administration?

A

SC > Oral > Topical

43
Q

Where does imidothiozoles distribute to?

A

All tissues, enters milk within an hour of SC adminstration

44
Q

How are imidothiosoles metabolized?

45
Q

How are imidothiozoles eliminated?

A

90% within 24 hours. 5 to 10% unchanged, in urine and feces. 60% by urine, 30% by feces.

46
Q

What are the adverse effects of imidothiozoles?

A

Stimulates nicotinic receptors in the host. Toxicity may be due to the muscarinic effects due to cholinesterase inhibition.

47
Q

What are the signs of imidothiozole toxicity?

A

Salivation, defecation, bradycardia, pupillary constriction, and respiratory distress

48
Q

At what dose do you start seeing imidothiozole toxicity?

A

2x’s the Effective dose

49
Q

What animal is most tolerant to imidothiozole?

50
Q

What animal is least tolerant to imidothiozole?

51
Q

How might there be an increase in toxicity with imidothiozole?

A

Use with pyrantel, morantel, or cholinesterase inhibitors

52
Q

How are the tetrahydropyrimidines eliminated?

A

Up to 40% in the urine. Because of this need to watch for renal status.

53
Q

How is the absorption like for tetrahydropyrimidines?

A

Poor, and only give PO. Maintained in the GI tract of ruminants for up to 98 days.

54
Q

How might one get better absorption of tetrahydropyrimidines?

A

Given with food

55
Q

What form of tetrahydropyridines do horses tend to tolerate best?

A

Tartrate salt > Pamoate salt

56
Q

Indications: Morantel

A

Gi worms (cows, sheep, and goats)

57
Q

Indications: Pyrantel

A

GI worms (swine, horse, dogs, and cats)

58
Q

What animals is piperazine used in?

A

Dogs, cats, horses, and pigs

59
Q

How does piperazine work?

A

GABA receptor agonist

60
Q

What does piperazine do to the worm?

A

Hyperpolarizes the muscles cells, makes them less responsive to signaling through micotinic acetylcholine receptors, causing flaccid paralysis of worm muscles

61
Q

What drug will piperazine compete with?

A

Tetrahydopyrimidines

62
Q

What part of the life cycle does piperazine not work against? Why?

A

Nematode egg, because it needs the nervous system to be developed in order for it to have an effect

63
Q

How is piperazine metabolized?

64
Q

How is piperazine eliminated?

65
Q

How is piperazine distributed in the body?

A

Most tissues except the fat

66
Q

What are the adverse effects of piperazine?

A

Dogs and cats. Emesis, diarrhea, ataxia, muscle tremors, behavior alteration, and head pressing

67
Q

What piperazine is used for heartworm prevention?

A

Diethylcarbamazine citrate, but it is no longer in use

68
Q

How does diethylcarbamazine citrate work?

A

Inihibits the production of PGE2 and PGI2. The worm induces the production of these in the host endothelium which inturn inhibits coagulation.

69
Q

What are the disadvantages of using diethylcarbamazine?

A

Requires daily dosing throughout the mosquito season. Only works against the larval stages

70
Q

When is melarsomine used?

A

Heartworm that is greater than 5 months of age.

71
Q

What are the adverse effects of melarsomine? How are they managed?

A

Injection site inflammation, coughing/gagging, vomiting, inappetence, lung congestion, fever, lethargy. This drug must be adminstered in a hospital setting where patient can be watched closely.

72
Q

How is melarsomine adminstered?

73
Q

What drugs does a nematode become resistant to if there is changes to the nicotinic receptors?

A

Levamisole and Pyrantel pamoate

74
Q

What drugs does a nematode become resistant to if there is changes to B-tubulin structure?

A

Albendazole

75
Q

What drugs does a nematode become resistant to if there is changes to p-gp?

A

Albendazole and Avermectins

Pharmacology II (20 decks)

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