warfarin

Generic Name: warfarin
Brand Name: Coumadin

Warfarin is an anticoagulant used in both human and veterinary medicine. In dogs, it is used primarily for long-term thromboprophylaxis. Current evidence does not support the use of warfarin in cats.

Despite it’s use in veterinary medicine, acute overdosages of warfarin may result in life-threatening hemorrhage.

It’s important to note that a lag time occurs after warfarin is ingested. It could, therefore, take 2-5 days before signs of toxicity occur.

Signs and symptoms of toxicity: extreme fatigue, refusal to eat, bloody urine, and vomiting. Due to the nature of warfarin’s mechanism of action, it may take 2-5 days before signs of toxicity occur. Animals should be monitored accordingly.

Toxic consumption: In both dogs and cats, doses of 5-50 mg/kg have been associated with toxicity.

Dogs: Warfarin Toxic Consumption
X-Small
Yorkie, Chihuahua
Small
Pug, Boston Terrier, Poodle
Medium
Beagle, Scottish Terrier
Large
Boxer, Cocker Spaniel
X-Large
Labrador & Golden Retrievers, German Shepherd
XX-Large
Great Dane, St. Bernard
1 – 10 lbs.
(0.45 – 4.6 kg)
11 – 25 lbs.
(5 – 11.4 kg)
26 – 40 lbs.
(11.8 – 18.2 kg)
41 – 70 lbs.
(18.6 – 31.8 kg)
71 – 90 lbs.
(32.3 – 40.9 kg)
91 – 110 lbs.
(41.4 – 50 kg)
dog1 dog2 dog3 dog4 dog7 dog6
> 2.25 mg > 25 mg > 59 mg > 93 mg > 161.5 mg > 207 mg

 

Cats: Warfarin Toxic Consumption
Most Cats

Large Cats
1 – 10 lbs.
(0.45 – 4.6 kg)
11 – 25 lbs.
(5 – 11.4 kg)
cat1 fat cat
> 2.25 mg > 25 mg

 

References:
– Papich MG. Saunders Handbook of Veterinary Drugs: Small and Large Animal. 3rd ed. St. Louis, MS: Elsevier Saunders; 2011.
– Warfarin Sodium. In: Plumb’s Veterinary Drugs. Tulsa (OK): Educational Concepts, L.L.C. [updated 8/14; accessed 8/27/15]. https://www.plumbsveterinarydrugs.com/#!/monograph/1721