Anthelmintics Flashcards
anthelminitic - define
A chemotherapeutic agent used to control
helminth infections
chemotherapy - define
Use of drugs to injure an invading organism
without injury to the host
classification of anthelminitics
spectrum of activity - broad vs narrow
chemical group/mode of action
target parasites
method of delivery/formulation
broad spec
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
potency is determined by ___
duration of exposure
potency
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
Imidazothiazoles/Tetrahydropyrimidines
yellow drench Imidazothiazoles -levamisole Tetrahydropyrimizines - pyrantel Cholinergic agonists - rapid and reversible spastic paralysis oral only
levamisole - target parasites
Gutworms +++ Adult +++ Mucosal larvae ++ Hypobiotic larvae + Lungworms +++
pharmacokinetics - levamisole
v.short half life in body
injection - 8h
oral - 14h
pour-on - 24h
macrolytic lactones (ML) - fermentation products
Avermectins - Streptomyces avermilitis
Milbemycins - Streptomyces cyanogriseus
macrolytic lactones (ML)
clear drench
avermectins + milbemycins
Open invertebrate specific glutamate-chloride channels in post-synaptic membrane leading to flaccid paralysis
macrolytic lactones (ML) - target parasites
Gutworms +++ Adult +++ Mucosal larvae +++ Hypobiotic larvae +++ Lungworms +++ arthropods ++
ML pharmacokinetics
long lasting - gives period of protection against re-infection - metaphylaxis
prevents pasture contamination - prophylaxis
roundwormers
benzimidazoles macrolytic lactones Imidazothiazoles + Tetrahydropyrimidines aminoacetile derivatives spiroindoles narrow spec - depsipeptides, salicylanilides, piperazines, phenylisothiocyanates
tapewormers
benzimidazoles
broad - tetrahydropyrimidines
narrow - isoquinolones, phenylisothiocyanates
praziquantel
isoquinolone
Tegument destruction
Increased membrane permeability for calcium-ions, loss of intracellular Ca++
spastic paralysis and malabsorption
flukicides
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
methods of delivery
oral - Drench, Paste, Tablet, in feed, Bolus (Intra-ruminal device)
parenterally - injection, subcutaneous, intramuscular
topical - tran-dermal, pour on
benzimidazoles
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