62. Ectoparasiticides – organophosphates, carbamates, pyrethroids

Question 1

what are Ectoparasiticides?

Answer 1

They are a class of antiparasitic drugs specifically designed to target and eliminate external parasites such as fleas, ticks, and mites

Question 2

organophosphates, Active substances

Answer 2

• Diazinon
• Phoxim
• Coumaphos

Question 3

organophosphates, mechanism of action

Answer 3

The organophosphates are irreversible inhibitors of acetylcholinesterase, an enzyme that breaks down acetylcholine, a neurotransmitter. By inhibiting this, acetylcholine builds up, causing an overstimulation of nerve receptors.
The drug is toxic upon contact!

Has a function on muscarinic ACh receptors, nicotinic ACh receptors and the central nervous system:

1. Muscarinic Ach receptors
They bind to acetylcholine and mediate various effects in the parasympathetic nervous system. Overstimulation leads to increased salivation, sweating and decreased heart rate

2. Nicotinic receptors
Also binds to acetylcholine. Overestimation leads to muscle twitching, cramps and potentially paralysis

3. Central nervous system
The drug affects the CNS, leading to neurological symptoms such as confusion, seizures and respiratory failure

Question 4

organophosphates, pharmacokinetics

Answer 4

1. Absorption
Good! Better oral than dermal
2. Distribution
Excellent
3. Elimination
80% in urine and 20% in faeces

Question 5

organophosphates, side effects

Answer 5

1. muscarinic ACh receptors
Salivation, lacrimation, urination, diarrhoea, GI-tract pain, vomiting

2. nicotinic ACh receptors
Muscle tremors, spasms

3. central nervous system
Seizures, coma, death

Question 6

organophosphates, indications

Answer 6

1. Diazinon
Fleas, ticks, lice, mites

2. Coumaphos
Varroosis of honey bees

Question 7

organophosphates, contraindications

Answer 7

NEVER give to cats !!! ⭢ toxic

Question 8

Carbamates, Active substances

Answer 8

• Propoxur

Question 9

Carbamates, mechanism of action

Answer 9

The carbamates are reversible inhibitors of acetylcholinesterase, which is an enzyme that breaks down acetylcholine, which is a neurotransmitter. By inhibiting this, acetylcholine builds up, causing an overstimulation of nerve receptors.

Question 10

Carbamates, toxicity

Answer 10

Much safer

Question 11

Carbamates, pharmacokinetics

Answer 11

Less lipophilic, oral vs dermal

Question 12

Carbamates, indications

Answer 12

Fleas and ticks

Question 13

Carbamates, administration

Answer 13

Collars
Aerosol spray
Shampoo

Question 14

pyrethroid, active substances

Answer 14

• Permethrin
• Deltamethrin
• Tetramethrin
• Flumethrin

Question 15

pyrethroid, mechanism of action

Answer 15

The pyrethroids will open the sodium channels, increasing the activity, leading to constant depolarisation, meaning that the nerve cells are constantly stimulated.

The immediate effect of the insecticide is a “knock-down” effect, causing the insect to become paralysed or unable to move.

Question 16

pyrethroid, indication

Answer 16

• Against ticks, mosquitoes and flies

Question 17

pyrethroid, administration

Answer 17

- Spot on lasts for 1 month
- Collar lasts for 8 months

Question 18

pyrethroid, toxicity

Answer 18

Generally safe for warm-blooded animals! But can however show side effects such as: tremors, seizures, excitation.
Fish is particularly vulnerable
There is no specific antidote

Question 19

pyrethroid, contraindication

Answer 19

NEVER use in cats as spot on, as it can lead to severe and potentially lethal effects!!

Question 20

pyrethroid, prognosis

Answer 20

generally good if treatment is administered promptly, with most cases resolving within 24 hours.