Anticoagulant rodenticide, otherwise most commonly known as “rat bait” poisoning, is a serious and potentially fatal toxicity that requires treatment. Coumarins such as warfarin and brodifacoum are the most commonly known examples. D-Con is a common rodenticide that pets ingest in the home in cases of toxicity.
Anticoagulant rodenticide is a vitamin K1 antagonist. Vitamin K is required for synthesis of clotting factors II, VII, IX, and X (2, 7, 9, and 10). Factor VII has the shortest half-life of these and will be depleted first.
Prothrombin time (PT) measures the extrinsic clotting system which contains factor VII and it becomes prolonged first. Therefore, PT measurement is helpful in determining clotting status in a pet that may have been exposed to anticoagulant rodenticide. Platelet counts in these animals are usually normal. Any time there is a history of potential exposure or an animal is showing evidence of bleeding, coagulation should be checked.
Pets that have been exposed to anticoagulant rodenticide are at risk for bleeding. They may bleed spontaneously or if they receive an injury could bleed due to their inability to clot. They can bleed from anywhere and symptoms may include melena, epistaxis, bleeding from gums, blood in urine or vomit, lameness or joint swelling, etc. Clinical signs may be seen initially within 4 to 6 days after ingestion.
If an animal is known to have recently ingested this toxin (within the last 8 hours), induction of emesis (vomiting) is recommended, followed by activated charcoal to prevent further absorption of the toxin, and supplemental Vitamin K 1 (phytonadione). It is given daily for 3 to 4 weeks. Vomit of this type of toxin is very commonly a green/blue color.
Animals that are actively bleeding will need supportive care which may include IV fluid therapy and blood products to provide clotting factors in addition to the Vitamin K1 supplementation.