Anticoagulant rodenticides Flashcards
What are the vitamin K dependent coagulation factors?
II, VII, IX, X
Which vitamin K dependent coagulation factor has the shortest half life?
VII
extrinsic pathway
What are the most common anti-coag rodenticides we see in vet med?
Second generation:
Brodifacoum
Bromodialone
Starting to see an increase in Bromethalin and Cholecalciferol rodenticides
How do pets get exposed to rodenticides?
Ingestion of baits, contaminated feed, sometimes relay or secondary toxicosis from ingesting a rat that died from the toxicant
What are some of the generalized properties of anti-coag rodenticides?
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
What generation of anti-coag rodenticides are the most toxic when ingested daily for about a week?
First generation
single does toxicity may be 50-100 times the multiple does toxicity
How long or how many doses does it take for second generation anti-coag rodenticides to be toxic?
second generation = effective after one dose
What animals are the most susceptible to anti-coag rodenticides and what species are most sensitive?
Dogs are most susceptible since they like to eat dumb stuff
Order of sensitivity: Pigs, dogs and cats, ruminants, horses and chickens
What factors may enhance the toxicity of anti-coag rodenticides?
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
How long does it take for anti-coag rodenticides to reach peak blood levels?
6-12 hours
*largely bound to plasma proteins
How are anti-coag rodenticides metabolized?
In the liver via hydroxylation
*highest concentrations in the liver
What generation of anti-coag rodenticides has the longest half life?
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
T/F: Anti-coag rodenticides can be excreted in the milk
True
can cross placental barrier
What is the MOA of anti-coag rodenticides?
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)
What clotting time lab test will be the first to be deplayed due to an anti-coag reodenticide?
PT = factor VII / extrinsic pathway
shortest half life
What clinical signs are associated with anti-coag rodenticides toxicosis?
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
What lesions are associated with anti-coag rodenticides?
Hemorrhage somewhere if this was the cause of death
bleeding every where - secondary bacterial pneumonia
What samples would be useful for chemical analysis?
Blood is perferred, serum, or plasma in a live animal
PM: liver, GI contets/vomitus, sample of bait
What coagulation tests will be prolonged with an anti-coag rat bait toxicosis?
PT (first) and PTT
PIVKA is another test that could be run potentially
APTT, ACT
Besides prolong coag times, what other lab findings will you see in a patient with anti-coag rat bait toxicosis?
Anemia
thrombocytopenia, hypoproteinemia (due to blood loss)
rads - may see evidence of hemorrhage
What factors are used to diagnose anti-coag rat bait ingestion?
hx, clinical signs, lesions (bleeding), bloodwork (CBC/PT/PTT), response to therapy
What is the first line of treatment for anticoag rodenticide toxicosis?
Vitamin K 1 therapy (Phytonadione) - PO
will start to work in 12-24 hours
need to treat current hemorrhage
T/F: if a patient is actively bleeding from rodenticide toxicosis it is best to start Vitamin K therapy IV
FALSE
this should never be given IV
PO is best. IM and SQ can be done
What will increase bioavailabiltiy of Vitamin K 1?
given with a fatty meal
If a patient vomits up a lot of rat bait, should they still be treated with Vitamin K?
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
What treatment should be done if a patient has had rodenticide exposure, is showing no clinical signs, but prolonged coag panel?
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
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?
15% or less; unstable patient - give blood and FFP
How soon after starting vitamin K therapy should you see an increase in coagulation times?
Improvement in 24 hrs
How do you determine the duration of vitamin K treatment in a pet that has ingested anticoag rodenticide?
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
What should be done after vitamin K therapy is completed?
Check PT 26-48 hours after the last vitamin K dose, +/- once more at 96 hours post final dose
What is the prognosis for patients that have ingested anticoag rodenticides?
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
