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Parasitology > Anthelmentics > Flashcards

Anthelmentics Flashcards

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1
Q

what is an anthelmentic and what are the two most important features of one

A

drug used to control parasites

  • spectrum of activity
  • safety index (ratio of toxic dose to therapeutic dose)
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2
Q

what class of drugs inhibit polymerization of tubulin formation in nematodes

A

benzimidazoles

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3
Q

what is a primary benzimidazole

A

thiabendazole (TBZ)

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4
Q

what are the 3 secondary benzimidazoles

A

cambendazole
parbendazole
oxibendazole

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5
Q

what are 3 tertiary benzimidazoles

A

Fenbendazole (FBZ)
albendazole (ABZ)
Oxfendazole (OFZ)

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6
Q

what can thiabendazole (TBZ) be used to treat

A 
broad spectrum (all gastro intestinal nematodes)
will kill migrating S vulgaris at 10X dosing rate
5 daily doses kills inhibited larvae of Ostertagia
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7
Q

what is the safety margin of TBZ

A

very high safety margin of above 10

non toxic

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8
Q

what are tertiary benzimidazoles used to treat

A

highly effective against inhibited ostertagia

currently in extensive use

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9
Q

what are some pharmacological features of the benzimidazoles

A

oral administration only- white drench
goes into rumen some gets to gut (depot effect)
metabolized to sulphoxidein liver->sulphone (anthelmentic activity)
OVICIDAL

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10
Q

what is the depot effect

A

metabolites of drugs also have anthelmentic effect

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11
Q

what species is benzimidazoles administered to and how

A

ruminants- drench
horses- paste
dogs, cats- tablets
pigs, poultry- powder

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12
Q

what is benzimidazole used to treat in ruminants

resistance?

A

tertiary
kills trichostrongyles and lungworms
kill inhibited and migrating larvae
widespread resistance in trichostrongyles in sheep

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13
Q

what is benzimidazole used to treat in horses

A

kill adult stages of all strongyles; kill migrating S. vulgaris larvae
NOT effective against inhibited cyathostomes (except when 5 daily doses used)
widespread resistance in cyathostomes

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14
Q

treatment with benzimidazole in dogs, cats, and pigs

A

no “depot”, must give 3-5 daily doses; mebendazole

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15
Q

what is imidazothiazoles- levamisole mode of action

A

cholinergic agonists at synaptic and extrasynaptic nicotinic acetylcholine receptors (motor end plates)
• depolarisation causes spastic paralysis
acting on the Nervous system

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16
Q

what does imidazothiazoles have activity against (worms)

A

nematodes including lung worms
not active against cestodes or trematodes
not active against inhibited larvae
Broad spectrum

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17
Q

how can imidazothiazoles be administered and what color is the drench

A

orally or parenterally, pour on (percutaneous absorbtion), intraruminally
clear drench

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18
Q

how does imidazothiazole act within the body

A 
rapidly absorbed from gut in ruminants and monogastrics
peak blood levels in 30 mins
excreted in urine in 6 hours
NOT ovicidal 
high safety index (easy to overdose)
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19
Q

is there resistance associated with imidazothiazole

A

widespread resistance in trichostrongyles of sheep and goats

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20
Q

which species are imidazothiazoles not used in and why

Study These Flashcards
A

horses- causes excitement

21
Q

Tetrahydropyrimidines - Morantel, Pyrantel mode of action

Study These Flashcards
A
  • depolarise motor end plates in muscle

* same site of action as levamisole (motor end plates)

22
Q

Tetrahydropyrimidines - Morantel, Pyrantel activity

Study These Flashcards
A
  • most GINs; NOT lungworms**

* NO effect on inhibited larvae**

23
Q

Tetrahydropyrimidines - Morantel, Pyrantel pharmacokinetics and safety index

Study These Flashcards
A 
• soluble
• administered orally
• rapidly absorbed
• excreted in urine
not ovicidal
SI: 7x
24
Q

Tetrahydropyrimidines - Morantel, Pyrantel use in sheep

Study These Flashcards
A

widely (?) used
resistance in trichostrongyles
cross resistance with levamisole
if resistant to morantel, still susceptible to levamisole

25
Tetrahydropyrimidines - Morantel, Pyrantel in cattle
``` morantel capsule (releases drug for 90 days) widely used in Europe resistance in trichostrongyles ```
26
Tetrahydropyrimidines - Morantel, Pyrantel use in horses
not effective against inhibited cyathostomes used as also effective against cestodes
27
Tetrahydropyrimidines - Morantel, Pyrantel use in dogs and cats
pyrantel rather than morantel used removes hookworms | often used with oxantel to kill whipworms
28
macrocyclic lactones mode of Action
GABA agonists- bind with high affinity to glutamate gated chloride channels ->flaccid paralysis
29
macrocyclic lactones actviity
all gastrointestinal nematodes and arthropods -not cestodes or trematodes extremely potent- very low dose is needed
30
macrocyclic lactones pharmacokinetics | and safety index
``` oral, injectable, pour-on absorbed rapidly short half life after oral admin half life of moxidectin is 28 days- long acting SI: 20x (very good) ```
31
what effects does administering ML orally have
high drug availability at site of parasite | improved therapeutic response
32
effects of administering ML parenterally/sub cutaneous
high drug systemic availability | extended persistence of antiparasitic acctivity
33
effects of administering ML as a pour on
large skin depot of the drug erratic percutaneous absorption oral ingestion large interanimal variability
34
what animals are MLs used in and against what
Sheep- widely used, limited resistance in trichostrongyles (cooperia and haemonchus) cattle: kills inhibited ostertagia, resistance only to cooperia horses: moxidectin kills up to 80%; resistance in cyathostomes dogs, cats: oral (milbemycin) or topical (selamectin)- lung and hookworms
35
what is the environmental effect of ML
persists in feces killing arthropods outside of host
36
what is the mode of action of OP
inhibits acetylcholinesterase- spastic paralysis
37
what is the activity of OP
highly effective against haemonchus | higher doses needed to kill trichostrongylus and ostertagia
38
where is OP used
only in sheep | there is no resistance present- so use in combo where resistance is an issue
39
what is the mode of action of piperazine
agonist of GABA receptors->flaccid paralysis | relies on peristaltic movement to remove worms
40
what is the activity of piperazine
narrow spectrum- ascarids and nodule worms given orally low toxicity
41
what animals is piperazine used in and against what
horses- removes adult strongyles, does not kill inhibited cyathostomes dogs, cats: effective against hookworms pigs: oesophagostomum spp.
42
what is the mode of action of closantel
uncouples oxidative phosphorylation
43
how is closantel given and how long does it persist
orally | in blood for 4-6 weeks
44
what species is closantel used in and against what
sheep- haemonchus, resistance limited but spreading | dogs: against hookworms, but rarely used
45
what is the mode of action of monepantel
nematode specific ACR 23 nicotinic acetylcholine receptor sub unit-> spastic paralysis
46
derquantel mode of action and what is it used for
nicotinic agonist-> flaccid paralysis- does not kill nematodes used in sheep against dictyocaulus
47
what treatments can be used against encysted larvae of small strongyles of horses
Fenbendazole @ 10mg/kg/day for 5 days Moxidectin @ 0.4 mg/kg
48
what should be the deworming regime for puppies
* treatment every 2 weeks prior to weaning * treatment every 4 weeks after weaning * treatment every 3 months after 6 months of age
49
what should be the deworming regime for pregnant bitches
• Fenbendazole @ 50 mg/kg/day from 3 weeks prepartum to 2-15 days postpartum

Parasitology (13 decks)

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