Phytonadione (Vitamin K1)
Phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone)
Also known as: K-Caps Β· Veda-K1 Β· Veta-K1 Β· K-Chews Β· K-Ject Β· Vita-Jec Β· Aqua-Mephyton Β· Konakion Β· Vitamine K1 Laboratoire TVM Β· Vitamin K1 Β· K-1 Β· methylphytylnaphthochinonum Β· phylloquinone Β· phytomenadionum Β· phytomenadione Β· Phytonadione Β· Methylphytylnaphthoquinone
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
π NA β North Americaπ EU β Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Adjunctive therapy of acute liver failure | 1-5 mg/kg PO or SC q24h | PO, SC | q24h | β | π NA |
| Anticoagulant rodenticide toxicity (exposed but non-bleeding) | 1.25-2.5 mg/kg PO twice daily with a fatty meal | PO | q12h | 2-4 weeks | π NA |
| Anticoagulant rodenticide toxicity (bleeding patient) | 2.5 mg/kg PO twice daily with a fatty meal | PO | q12h | minimum of 4 weeks | π NA |
| Anticoagulant rodenticide toxicity (symptomatic) | Loading dose of 2.5-5 mg/kg PO, then 3-5 mg/kg PO divided twice daily | PO | q12h | 14 days (1st gen) or at least 30 days (2nd gen/unknown) | π NA |
| Known 1st generation coumarin toxicity or vitamin K1 deficiency | initially 2.5 mg/kg s.c. in several sites, then 1-2.5 mg/kg in divided doses p.o. | SC/PO | q8-12h | 5-7 days | π EU |
| Known 2nd generation coumarin (brodifacoum) toxicity | initially 5 mg/kg s.c. in several sites, then 2.5 mg/kg p.o. | SC/PO | q12h | 3 weeks | π EU |
| Known inandione (diphacinone) or unknown anticoagulant toxicity | initially 2.5-5 mg/kg s.c. over several sites. Then 2.5 mg/kg p.o. divided | SC/PO | q8-12h | 3-4 weeks | π EU |
| Liver disease (pre-biopsy) | 0.5-1.0 mg/kg | SC | q12h | 1-2 days | π EU |
- Anticoagulant rodenticide toxicity (exposed but non-bleeding): Only give SC with starting dose if patient is vomiting or activated charcoal was administered.
- Anticoagulant rodenticide toxicity (bleeding patient): Plasma/blood transfusions are a necessity. Re-examine clotting times 2-3 days following cessation of therapy.
- Anticoagulant rodenticide toxicity (symptomatic): Check PT or PIVKA 48 hours after stopping therapy; if prolonged, continue for another week.
- Known 1st generation coumarin toxicity or vitamin K1 deficiency: Administer SC initially, followed by oral maintenance.
- Known 2nd generation coumarin (brodifacoum) toxicity: Restrict activity for 1 week post-treatment. Re-evaluate coagulation status 3 weeks after cessation of treatment.
- Known inandione (diphacinone) or unknown anticoagulant toxicity: Re-evaluate coagulation status 2 days after stopping therapy. If PT is elevated, continue therapy for 2 additional weeks. If normal, rest for 1 week.
- Liver disease (pre-biopsy): Re-evaluate coagulation time before biopsy. If minimal improvement, fresh frozen plasma may be required.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Adjunctive therapy of acute liver failure | 1-5 mg/kg PO or SC q24h | PO, SC | q24h | β | π NA |
| Anticoagulant rodenticide toxicity (exposed but non-bleeding) | 1.25-2.5 mg/kg PO twice daily with a fatty meal | PO | q12h | 2-4 weeks | π NA |
| Anticoagulant rodenticide toxicity (bleeding patient) | 2.5 mg/kg PO twice daily with a fatty meal | PO | q12h | minimum of 4 weeks | π NA |
| Anticoagulant rodenticide toxicity (symptomatic) | Loading dose of 2.5-5 mg/kg PO, then 3-5 mg/kg PO divided twice daily | PO | q12h | 14 days (1st gen) or at least 30 days (2nd gen/unknown) | π NA |
| Known 1st generation coumarin toxicity or vitamin K1 deficiency | initially 2.5 mg/kg s.c. in several sites, then 1-2.5 mg/kg in divided doses p.o. | SC/PO | q8-12h | 5-7 days | π EU |
| Known 2nd generation coumarin (brodifacoum) toxicity | initially 5 mg/kg s.c. in several sites, then 2.5 mg/kg p.o. | SC/PO | q12h | 3 weeks | π EU |
| Known inandione (diphacinone) or unknown anticoagulant toxicity | initially 2.5-5 mg/kg s.c. over several sites. Then 2.5 mg/kg p.o. divided | SC/PO | q8-12h | 3-4 weeks | π EU |
| Liver disease (pre-biopsy) | 0.5-1.0 mg/kg | SC | q12h | 1-2 days | π EU |
- Known 1st generation coumarin toxicity or vitamin K1 deficiency: Administer SC initially, followed by oral maintenance.
- Known 2nd generation coumarin (brodifacoum) toxicity: Restrict activity for 1 week post-treatment. Re-evaluate coagulation status 3 weeks after cessation of treatment.
- Known inandione (diphacinone) or unknown anticoagulant toxicity: Re-evaluate coagulation status 2 days after stopping therapy. If PT is elevated, continue therapy for 2 additional weeks. If normal, rest for 1 week.
- Liver disease (pre-biopsy): Re-evaluate coagulation time before biopsy. If minimal improvement, fresh frozen plasma may be required.
Small Mammals
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Anticoagulant rodenticide toxicity | 5 mg/kg/day divided q8-12h | PO | q8-12h | β | π NA |
| Anticoagulant rodenticide toxicity (symptomatic) | Loading dose of 2.5-5 mg/kg PO, then 3-5 mg/kg PO divided twice daily | PO | q12h | 14-30 days | π NA |
- Anticoagulant rodenticide toxicity: Give with a fatty meal (e.g., peanut butter). Do not give IV; SC can cause anaphylaxis.
- Anticoagulant rodenticide toxicity (symptomatic): Treat pocket pets at the high end of this dosage range.
Birds
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Hemorrhagic disorders | 0.25-0.5 mL/kg IM of the 10 mg/mL injectable product | IM | β | β | π NA |
| Hemorrhagic disorders | 0.2-2.5 mg/kg IM as needed | IM | as needed | usually only 1-2 injections required | π NA |
- Hemorrhagic disorders: Commonly used before surgery where hemorrhage is anticipated.
- Hemorrhagic disorders: May also be used prophylactically when amprolium and sulfas are administered.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Warfarin (or related compounds) toxicity | 500 mg SC q4-6h | SC | q4-6h | Until OSPT returns to normal | π NA |
| Warfarin (or related compounds) toxicity | 0.5-2.5 mg/kg IM, if IV use is necessary dilute in saline or D5W/saline and give very slowly (not to exceed 5 mg/minute) | IM, IV | β | β | π NA |
- Warfarin (or related compounds) toxicity: Whole blood or fresh plasma may also be necessary early in treatment.
- Warfarin (or related compounds) toxicity: Avoid IV if possible.
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Anticoagulant rodenticide toxicity | Initially 0.5-2.5 mg/kg IV in D5W at a rate of 10 mg/minute. Subsequent doses may be given IM or SC. | IV, IM, SC | β | 3-4 weeks for second generation agents | π NA |
| Anticoagulant rodenticide toxicity | 0.5-2.5 mg/kg IM, if IV use is necessary dilute in saline or D5W/saline and give very slowly (not to exceed 5 mg/minute) | IM, IV | β | β | π NA |
| Acute hypoprothrombinemia with hemorrhage | 0.5-2.5 mg/kg IV, not to exceed 10 mg/minute in mature animals and 5 mg/minute in newborn and very young animals | IV | β | β | π NA |
| Non-acute hypoprothrombinemia | 0.5-2.5 mg/kg IM or SC | IM, SC | β | β | π NA |
| Sweet clover or lespedeza toxicity | 1-1.5 mg/kg SC for several days | SC | q24h | several days | π NA |
- Anticoagulant rodenticide toxicity: Avoid IV if possible.
- Sweet clover or lespedeza toxicity: Remove from source, avoid stress/injury.
Swine
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Warfarin (or related compounds) toxicity | 0.5-2.5 mg/kg IM, if IV use is necessary dilute in saline or D5W/saline and give very slowly (not to exceed 5 mg/minute) | IM, IV | β | β | π NA |
- Warfarin (or related compounds) toxicity: Avoid IV if possible.
Sheep
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Warfarin (or related compounds) toxicity | 0.5-2.5 mg/kg IM, if IV use is necessary dilute in saline or D5W/saline and give very slowly (not to exceed 5 mg/minute) | IM, IV | β | β | π NA |
- Warfarin (or related compounds) toxicity: Avoid IV if possible.
Goats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Warfarin (or related compounds) toxicity | 0.5-2.5 mg/kg IM, if IV use is necessary dilute in saline or D5W/saline and give very slowly (not to exceed 5 mg/minute) | IM, IV | β | β | π NA |
- Warfarin (or related compounds) toxicity: Avoid IV if possible.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
βPhytonadione (Vitamin K1)β is a synthetic, lipid-soluble vitamin identical to naturally occurring Vitamin K1. It is a critical antidote in veterinary medicine, primarily utilized to reverse coagulopathies caused by the ingestion of anticoagulant rodenticides (e.g., warfarin, brodifacoum, bromadiolone).
Key clinical applications include:
- βAnticoagulant Rodenticide Toxicity:β The mainstay of therapy. Second-generation rodenticides have a very long half-life, often requiring 3-4 weeks of continuous Vitamin K1 supplementation.
- βSweet Clover Poisoning:β Used in ruminants to treat dicumarol toxicity from moldy sweet clover.
- βHepatic Disease:β Used adjunctively in acute liver failure or biliary obstruction where Vitamin K absorption or utilization is impaired.
- βSulfaquinoxaline Toxicity:β Reverses bleeding disorders associated with this coccidiostat.
βClinical Pearl:β Vitamin K1 (phytonadione) is effective for these toxicities, whereas Vitamin K3 (menadione) is ineffective and carries a higher risk of toxicity. Phytonadione requires 6-12 hours to synthesize new clotting factors; therefore, actively bleeding patients require immediate plasma or whole blood transfusions to provide active coagulation factors.
Mechanism of action
Phytonadione is essential for the hepatic synthesis of βVitamin K-dependent coagulation factors (Factors II, VII, IX, and X)β.
- βMechanism:β In the liver, inactive precursors of these factors require Ξ³-carboxylation of their glutamic acid residues to become functional. This carboxylation is catalyzed by the enzyme βΞ³-glutamyl carboxylaseβ, which requires the reduced form of Vitamin K (Vitamin K hydroquinone) as a cofactor.
- βThe Vitamin K Cycle:β During carboxylation, Vitamin K is oxidized to Vitamin K epoxide. The enzyme βVitamin K epoxide reductase (VKOR)β recycles the epoxide back to the active hydroquinone form.
- βAnticoagulant Rodenticides ββ inhibit VKOR, depleting active Vitamin K and halting the production of functional clotting factors. Exogenous phytonadione bypasses this blockade, providing the necessary substrate to resume factor synthesis.
Safety & warnings
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)
Adverse 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)
Precautions
βIntravenous Administration Warning:β 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.
βInjection Site Bleeding:β IM injections can cause acute bleeding at the site in coagulopathic patients. Use small-gauge needles for SC or IM injections.
βDelayed Onset:β 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).
βAbsorption:β 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
May decrease the numbers of Vitamin K-producing bacteria in the gut, though chronic therapy usually has no significant effect on phytonadione absorption.
Concomitant oral administration may reduce the GI absorption of oral Vitamin K.
Phytonadione directly antagonizes the anticoagulant effects of these drugs.
May prolong or enhance the effects of anticoagulants, thereby antagonizing some of the therapeutic effects of phytonadione.
Antagonizes the effects of vitamin K
Antagonizes the effects of vitamin K
Antagonizes the effects of vitamin K
Antagonizes the effects of vitamin K
Antagonizes the effects of vitamin K
Antagonizes the effects of vitamin K
Antagonizes the effects of vitamin K
Antagonizes the effects of vitamin K
Antagonizes the effects of vitamin K
Antagonizes the effects of vitamin K
Antagonizes the effects of vitamin K
May decrease gut flora production of vitamin K, though clinically minor when exogenous K1 is supplemented
May exacerbate bleeding tendencies through platelet inhibition
Monitoring
- Clinical efficacy (resolution or lack of hemorrhage, pale mucous membranes, weakness)
- One-stage prothrombin time (OSPT / PT)
- Proteins Induced by Vitamin K Absence (PIVKA)
- International Normalized Ratio (INR)
- Prothrombin time (PT) is the best method of monitoring therapy
- Prothrombin Time (PT) - typically normalizes within 12-24 hours of starting therapy
- Activated Partial Thromboplastin Time (aPTT)
- PIVKA (Proteins Induced by Vitamin K Absence or Antagonism)
- Clinical signs of bleeding (mucous membranes, heart rate, respiratory rate)
Pharmacokinetics
Half-life
Absorption
Absorbed from the GI tract via intestinal lymphatics, requiring bile salts. Oral absorption is significantly enhanced (4-5 times in dogs) when administered with fatty foods. SC or PO doses may be poorly absorbed in hypovolemic animals.
Distribution
Concentrates in the liver for a short period but is not appreciably stored in the liver or other tissues. Small amounts cross the placenta. Enters maternal milk.
Metabolism
Rapidly metabolized in the liver to polar metabolites.
Elimination
The exact elimination pathways of Vitamin K1 are not completely understood, but metabolites are excreted in bile and urine.
Overdose
Phytonadione is relatively non-toxic. It is highly unlikely that toxic clinical signs would result after a single overdosage. However, inappropriate routes of administration (like rapid IV injection) can cause severe anaphylactoid reactions regardless of the dose.
Available products
Formulations
- Oral capsules
- Oral chewable tablets
- Aqueous colloidal solution for injection
- Emulsion for injection
- Injectable: 10 mg/ml
- Oral: 50 mg tablets
- Nutraceuticals (containing small amounts)
- Injectable solution (10 mg/ml)
- Oral tablets (10 mg, 25 mg, 50 mg)
Veterinary
- Phytonadione Oral Capsules: 25 mg, 50 mg (K-Caps, Veda-K1, Veta-K1, Vitamin K1 Double Strength)
- Phytonadione Oral Tablets, Chewable: 25 mg, 50 mg (Vitamin K1 Chewable, K-Chews)
- Phytonadione Aqueous Colloidal Solution for Injection: 10 mg/mL (K-Ject, Veda-K1, Vita-Jec)
- Vitamine K1 Laboratoire TVM
- Konakion
- Vitamin K1 Injection (10 mg/ml)
- Vitamin K1 Tablets (10 mg, 50 mg)
Human-labeled
- Phytonadione Oral Tablets: 5 mg (Mephyton)
- Phytonadione Injection, Emulsion: 2 mg/mL & 10 mg/mL
- Konakion (Phytomenadione) injection (10 mg/ml)
- Konakion tablets (10 mg)
Regulatory status
Widely approved across EU member states for veterinary use.
Available as authorized veterinary medicines.
No regulatory data for: πΊπΈ US Β· ππ° HK Β· πΉπΌ TW Β· π―π΅ JP Β· π°π· KR Β· π¦πΊ AU
Storage & stability
Phytonadione is highly sensitive to light and must be protected from light at all times. Store tablets and capsules in well-closed, light-resistant containers. If used as an IV infusion, the container and tubing should be wrapped with an opaque material.
Client information
- βStrict Adherence to Schedule:β 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.
- βGive with Food:β 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.
- βExercise Restriction:β 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.
- βFollow-up Testing:β 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.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerβs current label.