Drugs Flashcards
Give an example of a repellent.
DEET
When might you use a repellent? What is an example?
To try keep biting flies (e.g stable fly) off horse e.g citronella
Give an example of a chlorinated hydrocarbon.
DDT, Lindane, Dieldrin
Give an example of an OP and it’s use in animals.
Dichlorovos - used in flea collars
Tichlorphon - oral use for Gastrophilus spp.
OPs persist for a long time in the environment, and may accumulate. True or false?
False
How do OPs work?
Inhibit Acetylcholine esterase
Which persists longer in the environment - carbamates or OPs?
Carbamates
How do carbamates work?
Inhibit ACh-ester ase
What is an example of a carbamate and its use in animals?
Carbaryl - powder or spray for flea control
What is the mechanism of action for formamidines?
Inhibit monoamine oxidase
What is an example of a formamidine and its use?
Amitraz - used in control of Rhiphicephalus australis
Which persists for longer in the environment - carbamates or pyrethroids?
Carbamates - pyrethroids degenerate after 24h
Why are synthetic pyrethroids more useful? What is one example and its use?
Longer half life.
E.g cypermethrin - backline treatment for lice in sheep
What are the three Avermectins? What bigger drug family do they belong to?
Ivermectin
Abamectin
Selamectin
ML’s
What is an example of a milbemycin?
Moxidectin
What is an example of a neo-nicitinoid and its mechanism of action?
Imidacloprid - blocks nicotinic Acetylcholine receptors
What class of chemical is Nitenpyram (capstar)?
A neo-nicitinoid
What is the active ingredient in Frontline and what chemical class is it?
Fipronil - a neo-nicitinoid
When might you use a growth regulator and what is one example?
Lufenuron - in a flea bomb
What is the mechanism of action for benzimadazole?
Inhibit polymerisation of tubulin
What generation and spectrum is thiabendazole?
Primary generation
Broad spectrum
Give an example of a secondary benzimidazole. What is the important difference between this and primary BZs?
Oxibendazole
Longer half life
Give an example of a tertiary benzimadazole and its use in animals
Fenbendazole
10x dose rate to kill migrating S. vulgaris larvae
5 daily doses to kill inhibited Ostertagia in cattle
Explain the ‘depot’ effect of BZ drugs in ruminants
Drug’s metabolites (e.g sulphoxide, sulphone)also have antihelmintic activity
After being absorbed across rumen, are metabolised and re-deposited into rumen where they can be re-absorbed again. Drug can have antihelmintic activity from lumen or from blood, in its original form or as a metabolite.
Are tertiary BZs effective against inhibited Cyathostominae in horses?
No
Are tertiary BZs effective at killing inhibited Ancyclostoma larvae in dogs?
No
Can you inject BZs?
No - insoluble
What is an example of an imidazothiazole?
Levamisole
How does levamisole work?
Agonist at cholinergic receptors to cause spastic paralysis
What is levamisole used for? Is there anything it doesnt cover, or any contraindications?
Treatment of all GINs and lungworms.
Ineffective against inhibited larvae and flatworms
Widespread resistance among trichostrongyles of sheep
Causes excitement in horses - not used
Is levimasole ovicidal?
No
Which has the wider safety margin - BZs or levimasole?
BZs. Levimasole safety index only 5
What are two examples of tetrahydropyrimidines?
Morantel, pyrantel
How does morantel work?
Depolarise motor end plates to cause spastic paralysis
Give two important differences between morantel and levimasole.
Morantel - can use on horses (good against cestodes).
Levimasole - can use on lungworms (morantel ineffective)
If a nematode becomes resistant to levamisole, it will also be resistant to ____ but not the other way around.
If a nematode becomes resistant to levamisole, it will also be resistant to morantel or pyrantel, but not the other way around.
Which tetrahydropyrimidine is more commonly used in dogs and cats? Which parasites is it good for?
Pyrantel
Hookworms and whipworms
How do macrocyclic lactones work?
Bind to glutamate-gated chloride channels with high affinity > increase Cl- conductance across cell membrane to cause flaccid paralysis > paralysed pharyngeal pump = cant eat, paralysed somatic muscles = can’t remain at predilection site
What are the three modes of administration for MLs?
Oral, injectible, pour-on
MLs are ___ safe and ____ potent than tetrahydropyrimidines.
MLs are more safe and more potent than tetrahydropyrimidines.
What is an advantage of each - oral - subQ and - topical (pour on) administration of MLs?
Oral: High drug concentration at intestinal site so good efficacy against GINs
SubQ: Flexible to modification with formula changes so can get extended activity
Pour on: Skin forms depot of drug for persistent action
Of the abomasal nematodes in sheep, which are mostly susceptible to MLs and which are resistant?
Haemonchus and Ostertagia are commonly resistant to MLs
Trichostrongylus usually susceptible
What is an important use for MLs in cattle? What is one example of a resistant nematode in cattle?
MLs can kill inhibited Ostertagia
Cooperia may be resistant
Can you kill all inhibited cyathostomes in a horse using Moxidectin?
No - usually about 80% killed
Give one example of a disadvantage of ML use.
Persists in dung so can kill arthropods (dung beetles) which means dung remains in environment longer
True or false: Haemonchus is more resistant than Ostertagia or Trichostrongylus to OPs?
False - Haemonchus is more susceptible, higher doses needed for the other two
Give an example of a heterocyclic compound and its use
Piperazine
Hookworms in dogs and cats
Oesophagostomum in pigs
Give an example of a salicylanilide and its use in animals
Closantel
Haemonchus contortus in sheep - best against blood feeders, can’t penetrate cuticle
How does closantel work?
Uncouples oxidative phosphorylation
What is an example of an octadepsipeptide and which animal might it be used in
Emodepside - dogs and cats
What class of drug is monepantel?
Amino-acetonitrile derivative
How does mopantel work?
Binds to nematode-specific nicotinic ACh receptor to cause spastic paralysis
How safe is mopantel? What dose do goats usually need compared to sheep?
Very safe - >30 safety index
Goats need double sheep dose
Which would you use against a Dictyocaulus infection in sheep - Monepantel or derquantel?
derquantel.
Monepantel ineffective against lungworms
How does derquantel work?
Nicotinic antagonist causing flaccid paralysis
What is the activity of derquantel like? Are there any species contraindications?
Not very effective against Ostertagia, oesophagostamum or chabertia. Medium spectrum - used in sheep in combination with abamectin.
TOXIC to horses
What are two acceptable protocols for killing of encysted Cythastominae larvae in horses?
Fenbndazole at 10mg/kg/day for 5 days
Moxidectin @ 0.4mg/kg
What is an acceptable protocol for treating a bitch for Ancyclostoma spp. encysted larvae, such that her puppies have the best possible protection from transmammary transmission?
fenbendazole at 50mg/kg/day from 3 weeks prepartum to 2-15 days post partum
