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Flashcards in Anthelmintics Deck (41):
1

Define anthemintic

Chemotherapeutic agent to control helminth infections

2

Define chemotherapy

Use of drugs to injure an invading organism without injury to the host (i.e. selective toxicity)

3

2 spectrums of activity

Broad or narrow

4

Chemical groups of anthelmintics - examples 3

Benzimidazoles (BZ) - fenbendazole
Imidaothiazoles (LM) - levamisole
Macrocyclic lactones (ML) - ivermectin

5

Classification of anthelmintics by target parasite

Nematodicide (roundworms)
Cestodicide (tapeworms)
Trematodicide/flukicide (trematodes/flukes)

6

How can anthelmintics be delivered? 3

Orally (drench, tablet, oral bolus)
Parentally (injection)
Topically (pour-on)

7

Overall classifications of anthelmintics -4

-spectrum of activity
-chemical group/mode of action
-target parasites
-method of delivery/formulation

8

Another name for group 1 benzimidazoles

White drenches

9

Another name for group 2 LM/imidazothiazoles

Yellow drenches

10

Another name for group 3 ML

Clear drenches

11

What are the 2 new groups of broad-spectrum anthelmintic

4 = AD = amino acetonitrile derivatives
5 = SI = spiroindoles

12

What are some examples of narrow spectrum anthelmintics

Fluke drenches, tapewormers, heartworms

13

Examples of benzimidazoles

Albendazole, Fenbendazole, Flubendazole, Mebendazole, Oxfendazole, Triclabendazole

14

Mode of action - BZ

Bind to parasite B-tubulin leading to inhibition of glucose uptake, glycogen depletion and death

15

Administration - BZ

Low water solubility - oral products only. Resuspend prior to administration

16

What determines BZ potency?

Duration of exposure (BZs kill worms very quickly)

17

3 ways to increase BZ potency?

1.) multiple low doses more potent than one single dose
2.) potency greater in ruminant/horse than dog (rumen/caecum acts as a reservoir)
3.) potency greater in ruminants if starved 12-24hr (slows rate of passage of ingesta)

18

Another name for Imidazothiazoles/yellow drenches

Tetrahydropyrimidines

19

Examples of Imidazothiazoles and Tetrahydropyrimidines

Imidazothiazoles - levamisole
Tetrahydropyrimidines - pyrantel

20

How do yellow drenches work?

Cholinergic agonists - cause a rapid and reversible spastic paralysis

21

Administration - yellow drenches

Only available as oral drenches.

22

What does levamisole act on?

Nematodes - especially adult gutworms, less so mucosal larvae and hypobiotic larvae. Also lungworms. NOT trematodes, cestodes, arthropods or protozoa.

23

Administration - levamisole? 3 How does this affect its pharmacokinetics?

Injection - rapid and high peak in plasma concentration, shorter duration of action
Oral - middle peak/duration
Pour-on longer half life, lowest plasma concentration

24

Examples of ML calsses - 2

Avermectins and Milbemycins

25

Mechanism of action - ML

Open invertebrate specific glutamate-chloride channels in post-synaptic membrane leading to flaccid paralysis

26

Spectrum of ML

Broad spectrum - targets all nematode gutworm and lungworm stages. Variable effects on arthropods. Not trematodes, cestodes or protozoa.

27

Pharmacokinetics of MLs

Oral/injection (highest peak) or pour-on.
Persistent effect provides period of protection against re-infection. Presistent activity used to design prophylactic worm control strategies.

28

Define metaphylaxis

Protection of animals grazing contaminated pasture

29

Define prophylaxis

preventing pasture infection (i.e. prevents autoinfection peak)

30

Name the roundwormers - 9

BROAD SPECTRUM:
-Benzimidazoles
-ML
-Imidazothiazoles/tetrahydropyrimidines
-Aminoacetile derivatives (new)
-spiroindoles (new)

NARROW SPECTRUM:
-desipeptides
-salicylanilides
-piperazines
-phenylisothiocyanates

31

What are monepantel and derquantel?

Examples of new broad spectrum anthelmintics

32

Name the roundwormers

BROAD SPECTRUM:
-benzimidazoles
-Tetrahydropyrimidines

NARROW SPECTRUM:
-isoquinolines
-phenylisothiocyanates

33

How does praziquantel (PZQ) work?

Tegument destruction (especially at the proliferation zone) --> increased membrane permeability for calcium ions, loss of intracellular calcium --> spastic paralysis and malabsorption. Ultimately the tapeworm is digested.

34

Flukicide - spectrum of action

Narrow spectrum target fluke and blood feeding nematodes. Some activity against blood sucking nematodes.

35

How do flukicides (salicylanilides and substituted phenols) work?

uncouple oxidative phosphorylation decreasing the availability of high energy phosphate compounds

36

Phamacokinetics - salicylanilides

Binds to plasma proteins --> prolonged plasma half life, not used in milking cattle or sheep.

37

What is the flukicide of choice for treating acute fasciolosis?

Triclabendazole (for treating flukes down to 2d old)

38

Define RDR

Recommended Daily Dose

39

What is fenbendazole (FBZ) active against?

(LS and SS) mucosal larvae

40

Define excipient

Other ingredients (as opposed to the acitve compound) that alter physical attributes and/or biological properties (e.g help transport drug through skin and into circulation)

41

3 main ways althelmintics can be delivered

By mouth (oral) - drench, paste, tablet, in feed, bolus
PN (injection) s/c, i/m
Topical (trans-dermal) - pour on

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