Vitamin K1 (Phytonadione)

What is this medication for?

• Anticoagulant rodenticide toxicity, other coagulopathies from vitamin K-dependent factor deficiency

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• Never give into a vein — this is the single most important safety point; use under the skin (preferred if not by mouth) or by mouth with a fatty meal.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Slow/poor absorption if under the skin/oral in hypovolemic patients

Worth a phone call to your veterinarian

• Acute bleeding at into a muscle injection site (Early in treatment, in coagulopathic patients)

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Anaphylactoid reaction after into a vein administration (Serious — this is why into a vein route is avoided)

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Hypersensitivity; does not correct hypoprothrombinemia due to hepatocellular damage (not the right tool for liver-failure coagulopathy)
• has or has had: FDA-CVM has warned against into a vein administration due to anaphylaxis risk — despite some older dosing references listing into a vein options, avoid this route; use small-gauge needles for under the skin/into a muscle

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Warfarin/other anticoagulant rodenticides
  • Mineral oil
  • Cephalosporins
  • Chronic oral antibiotics

Storage and handling

Protect from light at all times — phytonadione is light-sensitive; into a vein bags/lines must be wrapped in opaque material if used. Tablets/capsules in well-closed, light-resistant containers.

Good to know

• Never give into a vein — this is the single most important safety point; use under the skin (preferred if not by mouth) or by mouth with a fatty meal.
• For actively bleeding patients, phytonadione alone will NOT provide the 6–12h needed for new factor synthesis — give fresh frozen plasma/whole blood for the acute crisis, then start phytonadione for ongoing management.
• Duration of therapy depends on the specific anticoagulant — 2nd-generation (long-acting) rodenticides require a much longer course (up to 6 weeks) than 1st-generation compounds; if the specific product is unknown, treat as if 2nd-generation.