Flashcards in LEC 23 - Anti-Nematodals Deck (75):
How are definitive hosts most commonly infected with nematodes?
Consumption or via vector (ie. biting)
Why is it so hard to treat nematodes?
They are very intimately related with the GI tract and therefore making it hard to get to the worm.
What are the five types of anti-nematodals?
What are the two types of benzamidazoles?
Albendazoles and fenbendazole
What are the two types of imidathiazoles?
Levamisole and Tetramisole
What are the three types of tetrahydropyrimidines?
Pyrantel pamoate, Pyrantel tartrate, and Morantel tartrate
What are the two types of piperazines?
Piperazine and diethylcarbamazine
What drug is considered an arsenical?
How do benzimidoles work?
Inihibit microtubule polymerization by binding B-tubulin in all worm stages. Binding is reversible. Also there is a toxic effect on the parasites. Worms will DIE prior to elimination
How does benzimidoles cause a toxic effect on worms?
GI secretory defects, will reduce glucose uptake by the worm GI tract
How well are benximidoles absorbed?
Water insoluble compounds. Formulated as pastes, suspensions and pellets.
How do you increase the efficacy of benzimiadoles?
Increased time in the GI tract.
What are the absorption characteristics of benzimiadoles in ruminants?
Rumen is a reservoir. Mixing increases the time the drug spends in the rumen. Acid pH of abomasum solubilizes the drug and increases its solubility.
What is the dosing regime in cattle for benzimiadoles?
One dose followed by a possible second dose 4 to 6 weeks later
What are the absorption characteristics of benzimiadoles in monogastrics?
Absorption decreased due to quick time in GI Tract. Acid pH of stomach does help solubilize the drug somewhat.
What is the dosing regime in monogastrics for benzimiazoles?
Once every 24 hours for 3 days minimum (depends on the organism that is present)
How are benzamidazoles metabolized?
Liver. Which produces active metabolites.
What are the side effects of benzamidazole?
Hypersensitivity reactions to antigens from dying worms
Fenbendazole indications: Dogs
Roundworms, hookworms, whipworms, and tapeworms
Fenbendazole indications: Cats
Roundworms, hookworms, strongyloides, lung worms, and giardia
Fenbendazole indications: Cows
Lung worms, stomach worms, intestinal worms, Haemonchus
Fenbendazole indications: Horses
Strongyles, pinworms, and ascarids
What is a side effect of fenbendazole?
What is febantel?
Pro-fendendazole that is metabolized to fenbendazole following absorption
What animals is febantel used in?
Dogs and cats
What is within drontal plus?
Febental, pyrantel pamoate, and praziquantel
Indications for Albendazole: Cats and dogs
Indications for Albendazole: Cows
Liver flukes, stomach worms, intestinal worms, and lung worms
What is albendazole approved for used in besides cats, dogs, and cattle?
Sheep, goats, and rodents
What are the side effects of albendazole?
Aplastic anemia in dogs, cats, and possible humans. Potentially teratogenic
Because of albendazoles teratogenic effects what should be given instead?
Fenbendazole in pregnant animals
What are the two forms of dl-tetramisole?
l-tetramisole and d-tetramisole
What are the characteristics of l-tetramisole?
Anti-nematodal effects, but also has toxicity
What are the characteristics of d-tetramisole?
No anti-nematodal effects as well has having toxicity.
What is another name for l-tetramisole?
What is the mechanism by which Levamisole works?
Nicotinic receptor agonist. Stimulation of nicotinic receptors in worm muscles cause tetanic paralysis.
how are the worms rid of with the use of levamisole?
Come out in feces, alive
What animals is the use of levamisole not indicated in?
Horses, dogs, and cats
indications for the use of levamisole in cattle, sheep and goats?
Mature/larval lung worms, mature stages of GI worms
Indications for the use of levamisole in swine?
Mature stages of GI worms
How is imdiothiozoles administered? Which is preferred?
PO, Topical, or SC. Oral is preferred because of the destruction of meat.
What is the ranking of BA when it comes to the route of administration?
SC > Oral > Topical
Where does imidothiozoles distribute to?
All tissues, enters milk within an hour of SC adminstration
How are imidothiosoles metabolized?
How are imidothiozoles eliminated?
90% within 24 hours. 5 to 10% unchanged, in urine and feces. 60% by urine, 30% by feces.
What are the adverse effects of imidothiozoles?
Stimulates nicotinic receptors in the host. Toxicity may be due to the muscarinic effects due to cholinesterase inhibition.
What are the signs of imidothiozole toxicity?
Salivation, defecation, bradycardia, pupillary constriction, and respiratory distress
At what dose do you start seeing imidothiozole toxicity?
2x's the Effective dose
What animal is most tolerant to imidothiozole?
What animal is least tolerant to imidothiozole?
How might there be an increase in toxicity with imidothiozole?
Use with pyrantel, morantel, or cholinesterase inhibitors
How are the tetrahydropyrimidines eliminated?
Up to 40% in the urine. Because of this need to watch for renal status.
How is the absorption like for tetrahydropyrimidines?
Poor, and only give PO. Maintained in the GI tract of ruminants for up to 98 days.
How might one get better absorption of tetrahydropyrimidines?
Given with food
What form of tetrahydropyridines do horses tend to tolerate best?
Tartrate salt > Pamoate salt
Gi worms (cows, sheep, and goats)
GI worms (swine, horse, dogs, and cats)
What animals is piperazine used in?
Dogs, cats, horses, and pigs
How does piperazine work?
GABA receptor agonist
What does piperazine do to the worm?
Hyperpolarizes the muscles cells, makes them less responsive to signaling through micotinic acetylcholine receptors, causing flaccid paralysis of worm muscles
What drug will piperazine compete with?
What part of the life cycle does piperazine not work against? Why?
Nematode egg, because it needs the nervous system to be developed in order for it to have an effect
How is piperazine metabolized?
How is piperazine eliminated?
How is piperazine distributed in the body?
Most tissues except the fat
What are the adverse effects of piperazine?
Dogs and cats. Emesis, diarrhea, ataxia, muscle tremors, behavior alteration, and head pressing
What piperazine is used for heartworm prevention?
Diethylcarbamazine citrate, but it is no longer in use
How does diethylcarbamazine citrate work?
Inihibits the production of PGE2 and PGI2. The worm induces the production of these in the host endothelium which inturn inhibits coagulation.
What are the disadvantages of using diethylcarbamazine?
Requires daily dosing throughout the mosquito season. Only works against the larval stages
When is melarsomine used?
Heartworm that is greater than 5 months of age.
What are the adverse effects of melarsomine? How are they managed?
Injection site inflammation, coughing/gagging, vomiting, inappetence, lung congestion, fever, lethargy. This drug must be adminstered in a hospital setting where patient can be watched closely.
How is melarsomine adminstered?
IV or SC
What drugs does a nematode become resistant to if there is changes to the nicotinic receptors?
Levamisole and Pyrantel pamoate
What drugs does a nematode become resistant to if there is changes to B-tubulin structure?