Pharm 2- Anthelmintics 1

kelseyfmeyer's version from 2015-05-10 01:44


Question Answer
define Anthelmintic drugsDrugs used to kill and /or expel the parasitic helminths in the host animal
what are the two types of Anthelmintic drugs?(1) Vermifuges– expels the helminths (2) Vermicides– kills the intestinal parasite
how is the selectivity of anthelmintics? exceptions?usually very selective (safe), working on receptors/metabolic processes/accumulation exclusive to the parasite. BUT organophosphorous compounds & levamisole DO have risk for tox since they aren't only selective for parasite stuff
most anthelmintics can be used in all species, but levamisole is for only?ruminant species and pigs
most anthelmintics can be used in all species, but Praziquantel is for only?dogs, cats and horses
most anthelmintics can be used in all species, but Piperazine is for only?monogastric species (NO RUMIS)
most anthelmintics can be used in all species, but Salicylanilides, nitroxynil& clorsulon are for only?ruminant species
How do nematodes develop resistance to nematodicides?they develop resistance to the MOA!
how do you prevent the development of resistance against nematodicides? (2)(1) ROTATE TYPE OF NEMATODICIDE (so the MOA keeps changing...dont keep changing within the same group, eg, BZDs) (2) minimum frequency of tx!

Benzimidazoles (NEMATODES- GI AND LUNG)

Question Answer
benzimidazoles have what spectrum of activity? what is their safety margin?BROAD spectrum, WIDE margin of safety
what are the 2 Subclasses of benzimidazoles?Benzimidazole thiazole, Benzimidazole carbamates
what drugs are in the benzimidazole thiazole subclass?thiabendazole
what drugs are in the Benzimidazole carbamates subclass?albendazole, fenbendazole, mebendazole, oxfendazole
what are the drugs in the Probenzimidazole (PRO DRUG) category? what are they converted into?netobimin (converted to albendazole), and febantel (converted to fenbendazole)
BZD (benzimidazole) carbamates (describe their activity, and dose needed, and why this is so)possess greater anthelmintic activity--> EVEN LARVICIDAL!! Since stronger, need a lower dose. This strength is because they have... (1) enhanced receptor binding in parasites (2) decreased metabolic inactivation in host animal
which benzimidazole subgroup (carbamates or thiazoles) has larvacidal activity?CARBAMATES
what is the MOA of benzimidazole?BZD binds irreversibly to nematode beta-tubulin, prevents dimerization with alpha-tubulin and polymerization of tubulinoligomers into microtubules I.E., INHIBIT MICROTUBULE FORMATION (this is also selective for nematode tubulin not host)
how does resistance develop against benzimidazoles?development of beta-tubulin isotypes with lower affinity for BZDs
what is the absorption of benzimidazoles like? what inc. the bioavailability of BZDs?absorption is LIMITED. Presence of food in stomach increases the bioavailability of drug (ex- fenbendazole)
what is the plasma conc of benzimidazoles like? who has a higher systemic avail.?BZD level in plasma is always <1% of the dose administered, and RUMINANTS have higher systemic avail.
metabolism of benzimidazoles (general)hepatic!
metabolism of BZD carbamates is special how?(hepatic) they are converted into ACTIVE METABOLITES! first metabolized to sulfoxides, which are active and extend effectiveness, before being metabolized again to sulphones, which are inactive. (albendazole to albendazole sulphoxide) (fenbendazole to fenbendazole sulphoxide)
the metabolism of albendazole and fenbendazoleis more rapid in who?cattle and goats
which benzimidazole has poor metabolism and excreted unchanged in faeces?Mebendazole
benzimidazole Clinical efficacy depends on?effective concentration at the site of action in the parasite
how safe are BZDs?well tolerated (safe!)
what are the contraindications of BZDs? (which BZDs have which effects on who?) (2)(1) Substituted BZDs are not indicated during early pregnancy (2) Parbendazoleand cambendazoleproduces teratogenic effects in pregnant ewes (2ndto 4thweek of gestation)
how do you admin BZDs?ORAL!! (paste or suspension/powder or granules)--> rumis can be gradual release boluses
whats special about the probenzimidazoles?(netobimin and febantel) they have TWO active metabolites!!
which proBZD is used in Rumis and monogastrics, because it can be converted via hepatic enzyme AND ruminal microorganisms? explain how it differs in activity between the two sp.Netobimin! In RUMIS--> nematocidal and fasciolicidal activity. In MONOGASTRICS--> nematocidal & cestocidalactivity
netobimin metabolic path?netobimin--> albendazole--(hepatic oxidation)--> albendazole sulfoxide
who can have febantel?horse/dog/cat
febantel metabolic path?febantel-->fenbendazole--(hepatic oxidation)-->fenbendazole sulphoxide
what is vercom? effective against?Combination of febantel(nematodes) and praziquantel(cestodes)
what is Drontal Plus? for who against what?(25 mg febantel, 5 mg pyrantel pamoateand 5 mg praziquantel) in DOGS!! (effective against canine ascarids, hookworms, whipworms and Echinococcussp)
how safe is febantel?wide margin of safety
Febantel is effective against?GI and lung parasites
Febantel contraindications?Vercom paste and Drontal Plus are contraindicated in pregnant dogs and cats
can you use BZDs in birds?yes, for lung nematodes


Question Answer
levamisole is effective against what?GI and lung nematodes
levamisole routes of admin?oral, parenteral, OR topical!!! (nice!)
how is levamisole formulated, based on route of admin?ORAL= hydrochloride salt paste. INJECTABLE=phosphate salt
MOA of levamisole? (basic)(2)(1) depolarization neuromuscular blockade (2) acts as immunostimulator
how does levamisole work as a depolarization neuromuscular blockade?It acts as a ganglionic stimulant and a direct cholinergic drug--> it binds to nicotinic receptors of nematodes---> sustained mm contraction and subsequent paralysis
what is the speed of the absorption and excretion of levamisole? what is its pharmacodynamic action?RAPID absorption and secretion. pharmacodynamic action is of nicotinic and muscarinic effects
how can levamisole be adminstered?bolus/ drench/ feed additive/ SC injection/ topical pour-on
what special action can levamisole have, in who?in DOGS, can act as a Heartworm microfilaricide (along with being GI and LUNG nematodes)
how is the safety margin of levamisole?NARROW (but leva is 4 times more safe than tetramisole)
tox of levamisole in who? SHEEP! (salivation, lacrimation, head shaking, muscle tremors, mild excitability)
what is the safe route of levamisole for cats and dogs?oral
what can make a levamisole tox worse?simultaneous administration of pyranteltartrate/ cholinesterase inhibitor drugs
when is levamicole contraindicated?DAIRY COWS (goes into milk and no established withdrawal time)
what is the big ol' WARNING about levamisole for you?WEAR GLOVES! leva can have Percutaneous absorption (topical absorption) and cause agranulocytosis (LOW WBC count)

Tetrahydropyrimidines (NEMATODES)

Question Answer
Tetrahydropyrimidines are most effective against?GI nematodes
what two drugs do we care about in the tetrahydropyrimidines?pyrantel and morantel
pyrantel spectrum? for who?BROAD spectrum all species
what are the two forms pyrantel is available in?tartrate or pamoate salt
what solution causes pyrantel to lose potency?Aqueous solution undergoes photoisomerization -->loss of potency
MOA of pyrantel and morantel?depolarizing neuromuscular blocking agent in nematode parasites. Causes sustained muscle contraction followed by paralysis of worms. (MORE potent than acetylcholine)
Pyrantel tartrate--> how is the absorption? exceptions? speed of metabolism? excretion? sp. diffs?WELL ABSORBED (except in ruminants), it is rapidly metabolized (and does undergo first pass effect), and is excreted in Urine (DOGS) and Feces (RUMINANTS)
Pyrantel pamoate--> what worm does pamoate work on, and how come it's so good at this?poorly soluble in water--> decreased absorption from the gut--> drug reaches the lower intestine and acts on pinworms (this is the one banfield used)
which two drugs have a more potent NM blockade effect than ACh? (acetylcholine)pyrantel and morantel
what is in Drontal Plus for dogs?Pyrantel pamoate(5 mg/kg) + febantel(25 mg/kg) + praziquantel(5mg/kg)
what is in Drontal for cats?Pyrantel pamoate(20 mg/kg) + praziquantel(5 mg/kg)
what is in Heartgard 30 Plus? for who? effective against what?contains ivermectin(6-12 g/kg) + pyrantel pamaote(5-10 mg), for DOGS, effective against heartworms, hookworms and ascarids
why would you want to give pyrantel to a horse?effective against Anaplocephala perfoliata tapeworm (ileo-caecal junction tapeworms)
why would you want to give pyrantel to a cattle/sheep?it is effective against BZD RESISTANT STRAINS of Haemonchus contortus (barber pole worm) (GI worm)
safety of pyrantel salts?generally safe in all species EXCEPT FOR HORSES
contraindications of pyrantel salts? (2)(1) not indicated in severely debilitated animals (2) withdrawal period for food animals needed
what is morantel used for? (in who?). anything to note about food animals?RUMNANTS! GI nematodes! adult and immature stages. Withdrawal period needed
whats the route of admin she emphasized for morantel?Sustained release ruminal bolus (morantel slow release trilaminate bolus) <--cylindrical tri-walled cartridge
which is a safer drug-- pyrantal tartrate or morantel tartrate?MORANTEL IS SAFER

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