Anthelmintics

Question 1

anthelminitic - define

Answer 1

A chemotherapeutic agent used to control

helminth infections

Question 2

chemotherapy - define

Answer 2

Use of drugs to injure an invading organism

without injury to the host

Question 3

classification of anthelminitics

Answer 3

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

Question 4

broad spec

Answer 4

Benzimidazoles – β-tubulin binding 2-LV
Imidazothiazoles – ACh agonist*
macrocyclic lactones – modulate glutamate-gated chloride channels
Amino-acetonitrile derivatives – targets specific Hco-MPTL receptors*
Spiroindole – ACh antagonist

Question 5

potency is determined by ___

Answer 5

duration of exposure

Question 6

potency

Answer 6

multiple low doses more potent than 1 large one
potency greater in ruminant/horse than dog
potency greater in ruminants if starved for 12-24h

Question 7

Imidazothiazoles/Tetrahydropyrimidines

Answer 7

yellow drench
Imidazothiazoles -levamisole
Tetrahydropyrimizines - pyrantel 
Cholinergic agonists - rapid and reversible spastic paralysis 
oral only

Question 8

levamisole - target parasites

Answer 8

Gutworms +++ 
Adult +++ 
Mucosal larvae ++ 
Hypobiotic larvae +
Lungworms +++

Question 9

pharmacokinetics - levamisole

Answer 9

v.short half life in body
injection - 8h
oral - 14h
pour-on - 24h

Question 10

macrolytic lactones (ML) - fermentation products

Answer 10

Avermectins - Streptomyces avermilitis

Milbemycins - Streptomyces cyanogriseus

Question 11

macrolytic lactones (ML)

Answer 11

clear drench
avermectins + milbemycins
Open invertebrate specific glutamate-chloride channels in post-synaptic membrane leading to flaccid paralysis

Question 12

macrolytic lactones (ML) - target parasites

Answer 12

Gutworms +++ 
Adult +++ 
Mucosal larvae +++ 
Hypobiotic larvae +++ 
Lungworms +++
arthropods ++

Question 13

ML pharmacokinetics

Answer 13

long lasting - gives period of protection against re-infection - metaphylaxis
prevents pasture contamination - prophylaxis

Question 14

roundwormers

Answer 14

benzimidazoles
macrolytic lactones
Imidazothiazoles + Tetrahydropyrimidines
aminoacetile derivatives
spiroindoles
narrow spec - depsipeptides, salicylanilides, piperazines, phenylisothiocyanates

Question 15

tapewormers

Answer 15

benzimidazoles
broad - tetrahydropyrimidines
narrow - isoquinolones, phenylisothiocyanates

Question 16

praziquantel

Answer 16

isoquinolone
Tegument destruction
Increased membrane permeability for calcium-ions, loss of intracellular Ca++
spastic paralysis and malabsorption

Question 17

flukicides

Answer 17

Salicylanilides and Substituted Phenols
Narrow Spec – fluke and blood feeding nematodes
Uncouple oxidative phosphorylation decr the availability of high energy phosphate compounds - blocks energy availability

Question 18

methods of delivery

Answer 18

oral - Drench, Paste, Tablet, in feed, Bolus (Intra-ruminal device)
parenterally - injection, subcutaneous, intramuscular
topical - tran-dermal, pour on

Question 19

benzimidazoles

Answer 19

white drench
Albendazole, (Ricobendazole) Fenbendazole, Flubendazole, Mebendazole, Oxfendazole, Triclabendazole
bind to parasite tubulin - inhibits glucose uptake - starves parasite to death
low water solubility - oral only