Vitamin K therapy improves hemostasis in Vitamin K deficient patients. It is often initiated pending test results, but maintenance of vitamin K is not indicated for patients having diagnoses of thrombocytopenia, hereditary factor deficiencies, or DIC.

Anticoagulant rodenticide toxicities are the most common cause of severe vitamin K deficiency in dogs and cats. Vitamin K reverses the anticoagulant effect of rodenticides over a period of 24 to 48 hours from initiation of therapy. Other vitamin K deficient states include: biliary obstruction, intrahepatic cholestasis, intestinal malabsorption and chronic oral antibiotic administration.

Warfarin is a relatively short-acting rodenticide, and treatment for a total of 1 week usually is adequate.

1. Administer an initial dose of Vitamin K1 (Aquamephyton, Merck, Sharp, Dohme), 2.2 mg/kg SC.
2. Follow with a dose of 1.1 mg/kg SC, q 12h, until active bleeding subsides.
3. Then substitute an oral vitamin K1 preparation (Mephyton) at the same twice-daily dosage.

To treat toxicity from second-generation, or long-acting rodenticides (bromadiolone, brodifacoum, or diphacinone, pindone):

1. Initiate parenteral Vitamin K1 as for warfarin (2.2 mg/kg SC).
2. Administer Vitamin K1 at 1.1 mg/kg SC, q 12h until hematocrit value stabilizes and active bleeding subsides.
3. Maintain oral Vitamin K1 at 1.1 mg/kg PO q 12h for a total of 2 weeks.
4. Taper the maintenance dose by one-half every 2 weeks during treatment.
5. In order to prevent relapse, continue therapy for 6 weeks.

Vitamin K for preoperative prophylaxis should be given at 1.1 mg/kg SQ q. 12 h for 1 to 2 days before surgery.

Subcutaneous injection of Vitamin K1 is the preferred parenteral route of administration because intravenous Vitamin K1 can cause anaphylaxis, and hematomas may form at intramuscular sites. Vitamin K3 (Synkayvite, Roche) is not effective for treating rodenticide toxicity due to its delayed onset of action.

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