Lecture 43 - Antiparasitics II Flashcards
what is the mechanism of action for macrocyclic lactones (milbemycins)
bind to glutamate-chlorine channels
increase Cl- influx
Hyperpolarization and pharyngeal pump dysfunction cause flaccid paralysis and death
what do macrocyclic lactones (milbemycins) NOT treat
cestodes and trematodes
T/F: moxidectin is the most lipophillic endectocide agent
TRUE
ivermectin/moxidectin can be used to treat what animals
ruminants, horses, swine, dogs, cats
what is the secondary mechanism of action for ivermectin
potent agonist of GABA that sends inhibitory signals to motor neurons and results in paralysis
PgP substrates are
ivermectin, moxidectin, and abamectin
an MDR1 mutation does what
- increase Cmax
- decreased elimination
- higher brain concentrations (GABA signs)
describe the use of milbemycin oxime
heartworm preventative, hookworms, ascarids, and whipworms
what side effect could occur from milbemycin oxime use
cardiovascular shock due to dead microfilariae reaction
nematodes
“round worms”
cylindrical body
have body cavity
cuticle covers body
digestive tube ends at anus
trematodes
“flukes”
non-segmented body
lack body cavity
Have tegument body covering
Digestive tube ends in cecum
cestodes
Segmented body
lack a body cavity
Have tegument body covering
Lack digestive tube
insufficient drug diffusion in worm causes ____ treatment
ineffective
ruminants develop strong aquired immunity to monezia by
5–6 months
describe equine tapeworms
- typically 1” long segments
- requires intermediate host
- associated with recurrent colic episodes
T/F: flea control is key to treat tapeworms
TRUE
what is the mechanism of action for benzimadazoles
Binds to parasite B-tubulin causing disruption of cell growth and differentiation
benzimadazoles can be used to treat
horses, ruminants, dogs, cats, swine
what do taenicides cause
death to tapeworms in situ
what do taenifuges cause
tapeworm expulsion and paralysis
what is the mechanism of action of Isoquinolones
increased calcium due to change in membrane permeability causing spastic paralysis
what is the applied pharmacology of praziquantel
absorbed, metabolized in the liver and excreted in the bile
what animals can be treated with praziquantel
dogs (not puppies)
sheep (infeasible due to low bioavailability)
horse (w/ recurring colic)
what part of the trematode life cycle is more susceptible to therapuetics
adult flukes
what is the period from fluke infection to adult egg-laying stage in cattle
10-12 weeks
what are considerations for treating flukes
- Immature and mature stages of the life cycle are pathogenic
- Drug or immature form must reach effective concentrations in liver tissue
- Drugs/metabolites for mature forms must be eliminated in bile excretion
- Infected areas in bile duct/liver cause hyperplasia and surround with connective tissue, which may decrease drug penetration into fluke
what is the mechanism of action of benzenesulfonamide
Decreases glucose utilization and significant reduction in ATP in fluke; Damage to GI and tegment
what is the spectrum of benzensulfonamide (give spp and animals)
only trematodes
cattle, sheep, goats
T/F: there is a small difference between the therapeutic and toxic index of benzensulfonamides
FALSE - high therapeutic index
T/F: fenbendazole will not treat F. hepatica
TRUE
what is the mechanism of action for nitroimidazoles
metabolite disrupts DNA synthesis
why is nitroimidazole prohibited in food animals
mutagen/carcinogen
toxicity of nitroimidazoles causes
V+ and neurotoxicity
what can nitroiminidazoles treat
- giardia
- tritichomonas foetus
T/F: benzimidazoles is the drug of choice for giardia
TRUE
what is the mechanism of action of triazine derivatives
Acts on apicoplast present in parasite to stop biosyntehsis of some amino acids and starch storage.
what is the mechanism of action of sulfonamides
Inhibit folic acid synthesis required by bacteria
T/F: Sulfonamides are the drug of choice for roundworms
FALSE - coccidia
what is the mechanism of action for thiamine analogues
Competitive inhibition of active thiamine transport into parasite
Thiamine analogue chronic use can lead to
thiamine deficiency
thiamine analogues can treat what animals
chickens, turkey, pheasants, calves
what is the mechanism of action of polyether ionophores
Complex with Alkali metal cations and transport across cellular membranes = Changes internal osmotic condtions and kills parasite
polyether ionophores are toxic to what species
horse
