Pyrethrins and Pyrethroids

Question 1

Pyrethrins are extracts of what type of flowers?

Bonus: name the species.

Answer 1

Pyrethrum flowers.

Crysanthemum cinerariaefolium.

Question 2

What are Pyrethriods?

Answer 2

They are synthetic analogs of pyrethrins.

Question 3

Why were pyrethrins/pyrethroids replaced by OPs and Organochlorines after WW II?

Answer 3

OPs and Organochlorines were more stable for storage.

Question 4

T/F: Pyrethrins/Pyrethroids are very stable in air and light.

Answer 4

False. They are unstable in air and light.

Question 5

T/F: Type 1 Pyrethrins contain alpha-cyano moiety while Type 2 does not.

Answer 5

False. Type 1 does not contain alpha-cyano moiety. Type 2 does.

Question 6

What benefit is there to adding alpha-cyano moiety to Type 2 Pyrethrins?

Answer 6

It increases the insecticidal potency.

Question 7

Overall, pyrethrins and pyrethroids are mildly toxic to mammals but very toxic to ____ and _____.

Answer 7

Fish and birds.

Question 8

One way fish could be exposed is…

Answer 8

The neighbor’s dog that has been treated with a topical product goes swimming in your fish pond.

Question 9

One way cats are exposed is…

Answer 9

Idiot clients used a spot-on made for dogs on their cat.

Question 10

T/F concerning Pyrethrins and Pyrethroids toxicokinetics,
They are lipid soluble, rapidly metabolized by GIT, plasma, and liver, excreted in the urine, and ingestion is the most common route of exposure.

Answer 10

False. Dermal exposure is most common while ingestion and inhalation are possible but not as common.
The rest is true.

Question 11

T/F. The presence of the alpha-cyano moiety (Type 2) increases the rate of hydrolysis. (speeds up metabolism)

Answer 11

False. It decreases the rate of hydrolysis. (slows down metabolism)

Question 12

There are no residual effects of pyrethrins/pyrethroids meaning there is no __________ in tissues.

Answer 12

accumulation

Question 13

_________ ________ or _______ may be added to pyrethrins for synergistic effect. It’s function is to inhibit pyrethrin metabolism by insects.

Answer 13

Piperonyl butoxide or MGK-264

Question 14

Which of the following is NOT TRUE concerning Pyrethrin/Pyrethroid MoA:
A. They produces a “knockdown effect” in insects.
B. They delay closure of Na ion channels in the axonal membrane of the insect.
C. Adrenal effects include hypoglycemia.
D. Insect metabolism of Pyrethrins is slower than a mammal’s metabolism.

Answer 14

C is not true. Adrenal effects may result in HYPERglycemia.

Question 15

Which of the following concerning the MoA of pyrethrins/pyrethroids is TRUE:
A. “Knockdown effect” means the insect is dead, dead, dead.
B. Insect Na channels are ~100x more sensitive to pyrethrins than mammalian ones.
C. At low concentrations Type 2 pyrethrins also interfere with GABA.
D. Pyrethrins bind more strongly at lower temperatures.

Answer 15

D is true.
A => “knockdown effect” insect is still alive just unable to move.
B => They are ~1000x more sensitive.
C => They interfere with GABA at HIGH concentrations.

Question 16

Some dogs may show ‘_____ _________’ which is actually paresthesia that may occur as a topical hypersensitivity reaction or firing of sensory peripheral nerves.

Answer 16

‘acute paralysis’

Question 17

Which of the following concerning pyrethrin/pyrethroid diagnosis is NOT TRUE:
A. Dx is generally made with Hx, CS, and ruling out other causes.
B. There are no pathologic lesions.
C. Generally there are low tissue levels and they don’t correlate well with severity of CS.
D. For PM Dx the liver and spleen are the best tissues. to test.

Answer 17

D is not true. The liver and the BRAIN are the tissues to test.

Question 18

The most important thing to remember about skin decontamination is to keep the patient from becoming __________ as this would make the toxicity worse and prolong the CS.

Answer 18

hypothermic

Question 19

To control severe muscle tremors in px with pyrethrin toxicosis we can give them ________________.

Answer 19

Methocarbamol

Question 20

Name 3 drugs we could give to control seizures induced by pyrethrin toxicosis.

Answer 20

Diazapam, propofol, and barbiturates.

Question 21

Prognosis for pyrethrin/pyrethroid toxicosis is generally:
A. Poor.
B. Good.
C. Call the coroner.

Answer 21

B. Good!

Question 22

In humans (yuck!) metabolism/excretion of pyrethrins occurs within:
A. 12 hours.
B. 24 hours.
C. 36 hours.
D. 48 hours.

Answer 22

B. 24 hours.