Anticoagulant rodenticides

Question 1

What are the vitamin K dependent coagulation factors?

Answer 1

II, VII, IX, X

Question 2

Which vitamin K dependent coagulation factor has the shortest half life?

Answer 2

VII

extrinsic pathway

Question 3

What are the most common anti-coag rodenticides we see in vet med?

Answer 3

Second generation:
Brodifacoum
Bromodialone

Starting to see an increase in Bromethalin and Cholecalciferol rodenticides

Question 4

How do pets get exposed to rodenticides?

Answer 4

Ingestion of baits, contaminated feed, sometimes relay or secondary toxicosis from ingesting a rat that died from the toxicant

Question 5

What are some of the generalized properties of anti-coag rodenticides?

Answer 5

Odorless and tasteless
formulations are resistant in the environment for weeks to months

Action is slow - generally not less than 24-36 hours
**over 1 week for 1st generation

Question 6

What generation of anti-coag rodenticides are the most toxic when ingested daily for about a week?

Answer 6

First generation

single does toxicity may be 50-100 times the multiple does toxicity

Question 7

How long or how many doses does it take for second generation anti-coag rodenticides to be toxic?

Answer 7

second generation = effective after one dose

Question 8

What animals are the most susceptible to anti-coag rodenticides and what species are most sensitive?

Answer 8

Dogs are most susceptible since they like to eat dumb stuff

Order of sensitivity: Pigs, dogs and cats, ruminants, horses and chickens

Question 9

What factors may enhance the toxicity of anti-coag rodenticides?

Answer 9

Vitamin K deficiency
Preexisting liver dz
Enzyme inhibitors (slows metabolism of warfarin)
Any other concurrent factors that cause hemorrhage
Drugs that may displace anti-coagulant from binding site
Sterioids or thyroxine

Question 10

How long does it take for anti-coag rodenticides to reach peak blood levels?

Answer 10

6-12 hours

*largely bound to plasma proteins

Question 11

How are anti-coag rodenticides metabolized?

Answer 11

In the liver via hydroxylation

*highest concentrations in the liver

Question 12

What generation of anti-coag rodenticides has the longest half life?

Answer 12

Second generation compounds (Brodifacoum)

• need to tx for 3-4 weeks due to long half like
• warfarin (1st gen) only need to treat for one week

Question 13

T/F: Anti-coag rodenticides can be excreted in the milk

Answer 13

True

can cross placental barrier

Question 14

What is the MOA of anti-coag rodenticides?

Answer 14

Inhibiting vitamin K epoxide reductase - this enzyme is what will recycle Vitamin K

Without it, you get a depletion of vitamin K and the vitamin K dependent coagulation factors

(have to use up all the vitamin K in the body and current clotting factors before clinical signs arise)

Question 15

What clotting time lab test will be the first to be deplayed due to an anti-coag reodenticide?

Answer 15

PT = factor VII / extrinsic pathway

shortest half life

Question 16

What clinical signs are associated with anti-coag rodenticides toxicosis?

Answer 16

Onset of CS in 1-5 days

Signs of hemorrhage: epistaxsis, hematuria, bleeding into abd/thorax, weakness, shock etc (large volume bleeds)

animals may die without external evidence of bleeding

Question 17

What lesions are associated with anti-coag rodenticides?

Answer 17

Hemorrhage somewhere if this was the cause of death

bleeding every where - secondary bacterial pneumonia

Question 18

What samples would be useful for chemical analysis?

Answer 18

Blood is perferred, serum, or plasma in a live animal

PM: liver, GI contets/vomitus, sample of bait

Question 19

What coagulation tests will be prolonged with an anti-coag rat bait toxicosis?

Answer 19

PT (first) and PTT

PIVKA is another test that could be run potentially
APTT, ACT

Question 20

Besides prolong coag times, what other lab findings will you see in a patient with anti-coag rat bait toxicosis?

Answer 20

Anemia
thrombocytopenia, hypoproteinemia (due to blood loss)

rads - may see evidence of hemorrhage

Question 21

What factors are used to diagnose anti-coag rat bait ingestion?

Answer 21

hx, clinical signs, lesions (bleeding), bloodwork (CBC/PT/PTT), response to therapy

Question 22

What is the first line of treatment for anticoag rodenticide toxicosis?

Answer 22

Vitamin K 1 therapy (Phytonadione) - PO

will start to work in 12-24 hours

need to treat current hemorrhage

Question 23

T/F: if a patient is actively bleeding from rodenticide toxicosis it is best to start Vitamin K therapy IV

Answer 23

FALSE

this should never be given IV

PO is best. IM and SQ can be done

Question 24

What will increase bioavailabiltiy of Vitamin K 1?

Answer 24

given with a fatty meal

Question 25

If a patient vomits up a lot of rat bait, should they still be treated with Vitamin K?

Answer 25

Yes. it is better to be safe than sorry. Especially since you can’t know for sure how much was absorbed.. if you don’t, you should at least check a PT in 12 to 24 hours

Question 26

What treatment should be done if a patient has had rodenticide exposure, is showing no clinical signs, but prolonged coag panel?

Answer 26

Start vitamin K
Consider a FFP transfusion or cryosupernantant to replace coag factors

If the transfusion is not given - have to make sure the patient is NOT active etc bc they are at high risk for hemorrhage

Question 27

If a patient presents over 24 hours after ingesting an anticoag rodenticide, a PCV of what percent is going to make you consider a whole blood transfusion in conjunction with FFP?

Answer 27

15% or less; unstable patient - give blood and FFP

Question 28

How soon after starting vitamin K therapy should you see an increase in coagulation times?

Answer 28

Improvement in 24 hrs

Question 29

How do you determine the duration of vitamin K treatment in a pet that has ingested anticoag rodenticide?

Answer 29

Depends on the half life of the agent ingested

Warfarin (1st generation) - has a shorter half life so 1 week of tx

Brodifacoum (2nd generation) - has a longer half life - 4 weeks of therapy

***unknown agent - default to 3-4 weeks of treatment

Question 30

What should be done after vitamin K therapy is completed?

Answer 30

Check PT 26-48 hours after the last vitamin K dose, +/- once more at 96 hours post final dose

Question 31

What is the prognosis for patients that have ingested anticoag rodenticides?

Answer 31

Generally treatable - depending on where hemorrhage has occurred

**patients who have recovered will be at a higher risk if they are exposed to a rodenticide again within a few weeks- lower toxic dose