Lecture 24

Question 1

What is an example of a macro-cyclic lactone?

Answer 1

Ivermectin, Moxidectin, Selamectin, Eprinomectin, Abamectin

Question 2

What is the mechanism of action of the macrocyclic lactones?

Answer 2

1. Agonist at glutamate R & GABA gated chloride ion channels
2. Chloride influx
3. Hyperpolarisation
4. Flaccid Paralysis

Question 3

What is the spectrum of activity of the macrocyclic lactones?

Answer 3

“Broad spectrum” - nematodes and arthropods but not trematodes or cestodes

Question 4

What breeds of dog should the macrocyclic lactones not be used in?

Answer 4

Collies, Australian Shepherds, Old English Sheepdogs, Shetland Sheepdogs and Border Collies

Question 5

Briefly explain how the adverse consequences of the macrocyclic lactones occur in the host:

Answer 5

The side effects are a result of GABA agonist in the host. They only affect host if ML’s gain access to CNS through the BBB (happens in certain breeds. Signs resemble those of the GABAergic receptors

Question 6

What is the main reason that the use of organophosphates has been declining?

Answer 6

They are declining due to the toxicity of them.

Question 7

What is the mechanism of action of the organophosphates?

Answer 7

They are AChE inhibitors meaning more ACh at nicotinic receptors causing spastic paralysis

Question 8

What is an example of an organophosphate?

Answer 8

Napthalophos

Question 9

What is the spectrum of activity of the organophosphates?

Answer 9

Some of them can be very effective against helminths and arthropods.

Question 10

What signs would be observed with organophosphate toxicity?

Answer 10

muscarinic signs