Etiology

• Cats are less often poisoned by dogs, but poisoning may follow ingestion of poisoned rodents.
• Reported acute oral LD 50s for the cat:
  • Warfarin 5-30 mg/kg
  • Diphacinone 15 mg/kg
  • Brodifacoum >25 mg/kg.
  • Bromadiolone > 25 mg/kg.

Pathophysiology

• Anticoagulant rodenticides inhibit Vitamin K epoxide reductase, the enzyme involved in production of active vitamin K.
• Clotting factors II (prothrombin), VII, IX and X all require active vitamin K to function effectively.
• Factor VII has shortest half-life and is therefore first to be affected by anti-coagulant poisoning.
• Depletion of clotting factors results in coagulopathy and profuse bleeding following trauma.

• Short acting rodenticides (eg warfarin, coumafuryl and pindone) generally require multiple exposures before coagulopathy occurs and toxic effects may resolve after 7 to 10 days.
• Second generation (longer acting) rodenticides (eg diphacinone, brodifacoum and bromadiolone) may produce a coagulopathy after a single dose and toxic effects may persist for more than 3 weeks.
• Signs do not develop until body reserves of vitamin K have been depleted, ie >24 hours after ingestion of rodenticide.
• Toxicity may be potentiated by phenylbutazone, diphenylhydantoin, adrenocorticosteroids, and sulfonamides.

Timecourse

• Clinical signs of poisoning usually appear 3-5 days following ingestion.
• Morbidity/recovery related to site of hemorrhage.
• Death, if it occurs, is usually within 1-6 days.