Phytonadione (Vitamin K1)
Also known as: Mephyton, K-Caps, Veda-K1, Veta-K1, K-Chews, K-Ject, Vita-Jec, Aqua-Mephyton, Konakion, Vitamine K1 Laboratoire TVM, Vitamin K1, K-1
* **Strict Adherence to Schedule:** Because modern rat poisons (second-generation rodenticides) stay in the body for a very long time, it is critical to give this medication for the **entire duration** prescribed (often 3-4 weeks). Stopping early can result in sudden, life-threatening internal bleeding. * **Give with Food:** Administer oral Vitamin K1 with a **fatty meal** (like canned pet food, a small amount of cheese, or peanut butter) to significantly boost how much drug is absorbed into the bloodstream. * **Exercise Restriction:** Keep your pet quiet and strictly confined (leash walks only, no jumping or rough play) during therapy to minimize the risk of bruising or internal bleeding from minor bumps. * **Follow-up Testing:** Your veterinarian will likely need to recheck your pet's blood clotting times about 48 hours *after* the last dose of Vitamin K1 to ensure the poison is completely out of their system.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
What it is used for
- Adjunctive therapy of acute liver failure
- Anticoagulant rodenticide toxicity (exposed but non-bleeding)
- Anticoagulant rodenticide toxicity (bleeding patient)
- Anticoagulant rodenticide toxicity (symptomatic)
- Known 1st generation coumarin toxicity or vitamin K1 deficiency
- Known 2nd generation coumarin (brodifacoum) toxicity
- Known inandione (diphacinone) or unknown anticoagulant toxicity
- Liver disease (pre-biopsy)
- Warfarin (or related compounds) toxicity
- Warfarin (or related compounds) toxicity
- Warfarin (or related compounds) toxicity
- Warfarin (or related compounds) toxicity
How it is given
Possible side effects
- Anaphylactoid reactions (especially following IV administration)
- Acute bleeding from the injection site (IM administration during early stages of treatment)
- Slow or poor absorption from SC or PO routes in hypovolemic patients
- Anaphylactic reactions (following IV administration)
- Haemolytic anaemia (in cats when overdosed)
- Anaphylaxis (primarily with IV administration)
- Injection site reactions (pain, swelling)
- Hematoma formation at injection sites (due to underlying coagulopathy)
Cautions & contraindications
- Known hypersensitivity to phytonadione or its components
- Hypoprothrombinemia due to hepatocellular damage (Vitamin K cannot correct this if the liver cannot synthesize the protein precursors)
- Intravenous administration (relative contraindication due to anaphylaxis risk)
- Known hypersensitivity to phytomenadione
- Intramuscular administration in severely coagulopathic patients (risk of severe hematoma)
- **Intravenous Administration Warning:** The FDA-CVM warns against administering phytonadione IV due to a significant risk of severe anaphylactoid reactions. If IV use is absolutely necessary (e.g., severe bleeding with very high INR in large animals), it must be diluted and given extremely slowly. **Injection Site Bleeding:** IM injections can cause acute bleeding at the site in coagulopathic patients. Use small-gauge needles for SC or IM injections. **Delayed Onset:** It takes 6-12 hours for new clotting factors to be synthesized. Emergency needs for clotting factors in actively bleeding patients MUST be met with blood products (fresh frozen plasma or whole blood). **Absorption:** SC or PO doses may be poorly absorbed in hypovolemic animals. Oral absorption requires bile salts and is significantly enhanced (4-5x) by administering with a fatty meal.
Drug interactions
- Oral Antibiotics: May decrease the numbers of Vitamin K-producing bacteria in the gut, though chronic therapy usually has no significant effect on phytonadione absorption.
- Mineral Oil: Concomitant oral administration may reduce the GI absorption of oral Vitamin K.
- Warfarin (and other coumarin/indanedione anticoagulants): Phytonadione directly antagonizes the anticoagulant effects of these drugs.
- Phenylbutazone, Aspirin, Chloramphenicol, Sulfonamides, Diazoxide, Allopurinol, Cimetidine, Metronidazole, Anabolic Steroids, Erythromycin, Ketoconazole, Propranolol, Thyroid Drugs: May prolong or enhance the effects of anticoagulants, thereby antagonizing some of the therapeutic effects of phytonadione.
- Aspirin: Antagonizes the effects of vitamin K
- Chloramphenicol: Antagonizes the effects of vitamin K
- Allopurinol: Antagonizes the effects of vitamin K
- Diazoxide: Antagonizes the effects of vitamin K
- Cimetidine: Antagonizes the effects of vitamin K
- Metronidazole: Antagonizes the effects of vitamin K
Frequently asked questions
What is Phytonadione (Vitamin K1) used for in pets?
* **Strict Adherence to Schedule:** Because modern rat poisons (second-generation rodenticides) stay in the body for a very long time, it is critical to give this medication for the **entire duration** prescribed (often 3-4 weeks). Stopping early can result in sudden, life-threatening internal bleeding. * **Give with Food:** Administer oral Vitamin K1 with a **fatty meal** (like canned pet food, a small amount of cheese, or peanut butter) to significantly boost how much drug is absorbed into the bloodstream. * **Exercise Restriction:** Keep your pet quiet and strictly confined (leash walks only, no jumping or rough play) during therapy to minimize the risk of bruising or internal bleeding from minor bumps. * **Follow-up Testing:** Your veterinarian will likely need to recheck your pet's blood clotting times about 48 hours *after* the last dose of Vitamin K1 to ensure the poison is completely out of their system.
Is Phytonadione (Vitamin K1) safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
Worried about your pet?
Peqaboo’s AI helps you track symptoms, understand lab reports, and know when to see a vet.
Get the Peqaboo app