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Pharmacology > Parasitic Drugs > Flashcards

Parasitic Drugs Flashcards

1
Q

Treating cestode tissue cysts

A

NOTHING

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2
Q

Benzimidazoles

A

-benzene ring +imidazole ring= benzimidazole

-works on GI (and some lung) nematodes, some cestodes in GI and trematodes in liver
*less on trematodes because drug stays mostly in the GI which is not where the flukes are

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3
Q

Benzimidazole mechanism of action

A

Binds to parasite beta-tubulin subunit of microtubule
-disrupts parasite cell shape, division, motility, secretion, absorption

*also binds to mammalian tubulin but dissociates quickly so little effect
*efficacy linked with increased drug-parasite exposure time

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4
Q

Negative effects of Benzimidazole

A

Generally safe
-bone marrow hypoplasia and pancytopenia reported after high/prolonged dosing in dogs

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5
Q

Benzimidazole Absorption PK

A

-poorly water soluble (pastes, suspensions, granules)

-poor oral availability
>limited by solubility in GI tract and therefore stay in GI
>Ruminants= drugs go to rumen as reservoir; slowly released to intestines

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6
Q

Benzimidazole Distribution PK

A

Generally high but variable

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7
Q

Benzimidazole Metabolism and Excretion PK

A

Metabolism:

  1. hepatic (CYP enzymes)
    -1st pass effects if oral absorption occurs
  2. Other tissues (lung, intestines)
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8
Q

Fenbendazole formulations

A

Fenbendazole (Panacur)
-DIN number, so can be used off label
-Horses: suspensions, pastes, granules
-Cattle: suspensions, feed premixes
-Swine, chickens, turkeys: Panacur
-Dogs: Panacur granules

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9
Q

Fenbendazole uses

A

-wide range of nematodes
-strongyles, ascarids, whipworms, hookworms, pinworms
-cestodes (Taenia claim in dogs

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10
Q

Fenbendazole off label use

A

-Small ruminants (sheep and goats)
-Cats: nematodes, giardia, lungworm (Aelurostrongylus)
-Birds, reptiles, exotics

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11
Q

Febental

A

-fenbendazole pro drug

-led to Drontal Plus (febental, pyrantel, praziquantel for tapeworms)

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12
Q

Albendazole

A

-Tradename= Valbazen
-oral suspension for cattle
-used for some adult flukes (Fasciola hepatica), adult cestodes, GI and lung nematodes

**gets into bloodstream..probabily why it works with flukes BUT
**potential teratogenic early in gestation… don’t use within 21 days of breeding

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13
Q

Triclabendazole

A

-Tradename= Fascinex
-active against adult and juvenile F.hepatica AND other flukes (F. magna, Paragonimus)
**juveniles are the ones making tracts through liver

Not licensed in Canada, but possible for Emergency Drug Release

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14
Q

Emergency Drug Release

A

to permit the manufacturer of a new drug to sell a limited quantity of the new drug to a vet
*used for diagnosing or treating a medical emergency

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15
Q

Foreign drug eligibility for foreign drug release

A
  1. medication used to treat serious disease
  2. medication not marketed in Canada
  3. documented clinical efficacy and target animal/human safety data are available (not just reports from VIN)
  4. there are no comparable products available
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16
Q

What products are not available foe emergency drug release?

A

-Biologics (vaccines or antitoxins)
-investigational drugs not approved elsewhere
-products where there are comparable product in Canada. *cost and ease of use and not valid reasons
-not used for pharmaceutical companies circumventing vet drug approval process

17
Q

Macrocyclic lactones

A

-Avermectins
-Milbemycins

*endectocides (kill both internal and external parasites
*related to macrolide antibiotics but no real antimicrobial activity
-come from Streptomyces in soil

18
Q

Avermectins

A

-Ivermectin
-Selamectin (small animal)
-Eprinomectin (dairy cows, but no access to milk)

19
Q

Milbemycins

A

-Moxidectin
-Milbemycin

20
Q

Macrocyclic lactone mechanism of action

A

-Activate glutamate-gated Cl channel allowing Cl entry
-causes flaccid paralysis in worm (pharyngeal muscles and somatic muscles). They let go and are flushed out

21
Q

Macrocyclic lactone effect on mammals

A

-At high concentrations, may bind with GABA receptors causing flaccid paralysis issues

22
Q

Macrocyclic lactone use

A

-used for nematodes and arthropods.
*no cestodes or trematodes
*no Demodex mites, or adult heartworm

-heartworm prevention (very small dose needed to prevent and work against larvae)

23
Q

Macrocyclic lactone PK

A

-oral, topical, injectable products
*note: pour ons on cows, means others non treated will also receive orally when they lick each other
-oral or transcuticular absorption by parasite

-lipophilic, high VD, wide distribution in tissues

-hepatic metabolism, mostly excreted via bile/feces

-elimination half life: 1-3 weeks
*watch withdrawal times (very long)
*will go to milk

24
Q

Long acting Macrocyclic Lactones

A

-Ectoparasites: Give them, kill the adults, then eggs will hatch later on and be killed as well

-Worms: can also be beneficial, but may need better management skills such as moving animals from infected pastures

25
Q

Adverse events of Macrocyclic lactones

A

Generally safe (mammals, reptiles, birds)
BUT can see Toxicity: associated with GABA stimulation in CNS= neuro signs (ataxia, seizures)

26
Q

Treatment of macrocyclic lactone toxicity

A

Supportive care
-IV lipid emulsion possible
-otherwise just wait it out

27
Q

Natural protection from macrocyclic lactone

A

P glycoprotein that keeps it out of CNS
-Certain dogs (Collies; white feet don’t treat) have a mutation for P glycoprotein allowing for drug to reach CNS

28
Q

Ivermectin (Ivomec) versions

A

Generic versions
-Oral drench for sheep
-Oral paste: horses
-Pour on: cattle
-Injectables: cattle, sheep, swine
-Oral pre mix: swine
-Oral tablet: dogs (for heartworm prevention, with pyrantel for deworming)

29
Q

Eprinomectin

A

Eprinex pour on:
Licensed for dairy cattle (not in Goats so can get in milk)
-no milk withholding time
-Maximum Residue Limit (MRL) in milk (acceptable limit)

Long Range SC injection:
NOT in DAIRY COWS
-a rapid and slow solvent carrier
-4-5mth activity against some worms
-4mth meat withdrawal period

30
Q

Dairy cow Ivomec vs. Eprinex

A

Eprinex has no milk withholding time

Ivomec cannot be used because milk withholding time

31
Q

Selamectin (Revolution)

A

-monthly topical formulations for cats and dogs
-systemic (bites) and topical (spread throughout coat)
-used for fleas, mites (not demodex), nematodes, heart worm. Minimal efficacy for ticks

-less affinity for p-glycoprotein so safer for ABC-B1 mutants

-interest for use in aquaculture for sea lice

32
Q

Moxidectin

A

Similar to Ivermectin

Types:
1. Quest(just moxidectin)/QuestPlus (praziquantel added…but tapeworms not a huge issue in horses)
-horses

  1. Advantage Multi (dogs, cats, ferrets)
    -Moxidectin +imidacloprid
  2. ProHeart6- sustained release in dogs for HW protection
33
Q
A
34
Q

Milbemycin

A

-small animals
-monthly tablets

Types:
1.Milbemax: adds praziquantel for cats tapeworms

  1. Interceptor- dogs and cats

3.Sentinel tablets- dogs

  1. Trifexis tablets-dogs

5.Nexgard spectra- dogs

35
Q

Macrocyclic lactone resistance

A

-huge issue in sheep
-some in cattle/horses

**widely in cyasthostomes and small strongyles

36
Q

Resistance mechanism of macrocyclic lactones

A

-induction of parasite efflux pumps (P-glycoproteins)
-changes in Glu-gated Cl channels

NEED to test for resistant parasites= Fecal egg count reduction test (pre and post treatment egg counts)
*resistance if not at least 95% reduction

37
Q

Ecological impact of macrocyclic lactones

A

-Avermectins persist in feces for long time
-can kill insects that degrade feces (eg. dung beetle)

38
Q

How to mitigate ecological impact from macrocyclic lactones?

A

Drug needs to be completely metabolized or excreted in different form

39
Q

Topical tips for macrocyclic lactones

A

-Apply to skin! Not the hair!

  • decreased efficacy if applied at very low temperatures

-flammable (watch while branding)

Pharmacology (33 decks)

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