# Phytonadione (Vitamin K1): veterinary dose and monograph

> Phytonadione (Vitamin K1) is a veterinary drug. Antidote for anticoagulant rodenticide toxicosis (brodifacoum, bromadiolone, difenacoum, warfarin etc.) — the most common cause of acquired coagulopathy in small-animal emergency practice. Indications include anticoagulant rodenticide toxicosis (first / second / third generation); adjunctive therapy of acute liver failure; hereditary coagulation factor deficiency adjunct. This monograph lists 13 reference doses for dogs, cats, cattle, horses, goats and sheep and 4 more species, each with route, frequency and source, plus meat and milk withdrawal periods for food animals.

Source: https://vetmasterji.com/drugs/phytonadione · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Veterinary drug
- **Also known as:** Vita-K, Mephyton, AquaMephyton
- **Species with doses:** Dogs, Cats, Cattle, Horses, Goats, Sheep, Pigs, Birds, Rabbits and Small mammals
- **General dose range:** 0.25–5 mg/kg PO q12h × 2–4 weeks (rodenticide protocol) — check the species tables for the indication
- **Routes:** PO, SC, IM
- **Last reviewed:** 1 October 2026

## Indications

- Anticoagulant rodenticide toxicosis (first / second / third generation)
- Adjunctive therapy of acute liver failure
- Hereditary coagulation factor deficiency adjunct
- Bile obstruction → fat-soluble vitamin malabsorption (Vit K deficiency)
- Newborn ruminant haemorrhagic disease (sweet clover ingestion in dam)

## Phytonadione (Vitamin K1) dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Dogs

*Phytonadione (Vitamin K1) doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Anticoagulant rodenticide — first generation | 1.25–2.5 mg/kg | PO | q12h | 14 days |
| Anticoagulant rodenticide — second generation (brodifacoum) | 1.25–2.5 mg/kg | PO | q12h × 2–4 weeks | at least 4 weeks (≥30 days) |
| Acutely bleeding patient — SC for rapid effect | 1.25–2.5 mg/kg | SC | first dose only, then PO | — |

- Anticoagulant rodenticide — first generation: Plumb’s p.976 (Merola 2002): first-generation anticoagulants — 14 days of vitamin K1 is usually sufficient; 1.25–2.5 mg/kg PO twice daily with a fatty meal (Talcott 2008). Papich 5e: short-acting rodenticides 1 mg/kg/day SC or PO for 10–14 days. Check PT 48 h after the last dose.
- Anticoagulant rodenticide — second generation (brodifacoum): Plumb’s p.976: bleeding patients 2.5 mg/kg PO twice daily with a fatty meal for at least 4 weeks (Talcott 2008); second-generation or unknown anticoagulant — at least 30 days (Merola 2002). Papich 5e: long-acting rodenticides 2.5–5 mg/kg/day for 3–4 weeks. Recheck PT 48–72 h after stopping; continue another week if prolonged. Typical oral range 1.25–2.5 mg/kg q12h (Papich 5e: 2.5–5 mg/kg/day).
- Acutely bleeding patient — SC for rapid effect: Plumb’s p.976: oral dosing is preferred; give the starting dose SC only if the patient is vomiting or activated charcoal has been given. Never IV (anaphylaxis). Plasma transfusion is needed for active haemorrhage — vitamin K1 takes 6–12 h to act. Starting dose 1.25–2.5 mg/kg SC with small needles at several sites.

### Cats

*Phytonadione (Vitamin K1) doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Anticoagulant rodenticide | 1.25–2.5 mg/kg | PO | q12h × 2–4 weeks | — |

- Anticoagulant rodenticide: Plumb’s p.976 (dogs and cats): 1.25–2.5 mg/kg PO twice daily with a fatty meal — 14 days for first-generation, at least 30 days for second-generation or unknown agents. Papich 5e: 1 mg/kg/day for 10–14 days (short-acting) or 2.5–5 mg/kg/day for 3–4 weeks (long-acting).

### Cattle

*Phytonadione (Vitamin K1) doses for cattle*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Sweet clover poisoning (moulded dicoumarol) | 1–1.5 mg/kg | SC | q24h for several days | — | Withdrawal NOT established — treat as extra-label |
| Anticoagulant rodenticide toxicity | 0.5–2.5 mg/kg | IM | repeat as needed (3–4 weeks for 2nd-generation) | — | Withdrawal NOT established — treat as extra-label |

- Sweet clover poisoning (moulded dicoumarol): Plumb’s p.976 (Oehme 2009): sweet clover or lespedeza toxicity 1–1.5 mg/kg SC for several days; remove the source and avoid stress. WITHDRAWAL — Plumb’s: the labelled injection carries no withdrawal times.
- Anticoagulant rodenticide toxicity: Papich 5e and Plumb’s p.976 (Upson; Veda-K1 label): 0.5–2.5 mg/kg IM or SC. For acute haemorrhage IV only if essential — diluted, no faster than 10 mg/min in adults, 5 mg/min in young animals. Second-generation agents may need 3–4 weeks (Bailey 1986).

### Horses

*Phytonadione (Vitamin K1) doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Anticoagulant rodenticide | 0.5–2.5 mg/kg | SC | repeat until PT normal | — |

- Anticoagulant rodenticide: Papich 5e: horses 0.5–2.5 mg/kg SC or IM. Plumb’s p.976: 0.5–2.5 mg/kg IM (Upson 1988); 500 mg TOTAL SC q4–6h until prothrombin time returns to normal (Byars 1987). Avoid IV; if unavoidable, dilute and give no faster than 5 mg/min.

### Goats

*Phytonadione (Vitamin K1) doses for goats*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Warfarin-type toxicity | 0.5–2.5 mg/kg | IM | repeat as needed | — | Withdrawal NOT established — treat as extra-label |

- Warfarin-type toxicity: Papich 5e and Plumb’s p.976 (Upson 1988): sheep and goats 0.5–2.5 mg/kg IM or SC; if IV is unavoidable, dilute and give no faster than 5 mg/min.

### Sheep

*Phytonadione (Vitamin K1) doses for sheep*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Warfarin-type toxicity | 0.5–2.5 mg/kg | IM | repeat as needed | — | Withdrawal NOT established — treat as extra-label |

- Warfarin-type toxicity: Papich 5e and Plumb’s p.976 (Upson 1988): sheep and goats 0.5–2.5 mg/kg IM or SC; if IV is unavoidable, dilute and give no faster than 5 mg/min.

### Pigs

*Phytonadione (Vitamin K1) doses for pigs*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Warfarin-type toxicity | 0.5–2.5 mg/kg | IM | repeat as needed | — | Withdrawal NOT established — treat as extra-label |

- Warfarin-type toxicity: Plumb’s p.976 (Upson 1988): swine 0.5–2.5 mg/kg IM; if IV is unavoidable, dilute and give no faster than 5 mg/min.

### Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

*Phytonadione (Vitamin K1) doses for buffalo*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Sweet clover poisoning (moulded dicoumarol) | 1–1.5 mg/kg | SC | q24h for several days | — | Withdrawal NOT established — treat as extra-label |
| Anticoagulant rodenticide toxicity | 0.5–2.5 mg/kg | IM | repeat as needed (3–4 weeks for 2nd-generation) | — | Withdrawal NOT established — treat as extra-label |

- Sweet clover poisoning (moulded dicoumarol): Plumb’s p.976 (Oehme 2009): sweet clover or lespedeza toxicity 1–1.5 mg/kg SC for several days; remove the source and avoid stress. WITHDRAWAL — Plumb’s: the labelled injection carries no withdrawal times.
- Anticoagulant rodenticide toxicity: Papich 5e and Plumb’s p.976 (Upson; Veda-K1 label): 0.5–2.5 mg/kg IM or SC. For acute haemorrhage IV only if essential — diluted, no faster than 10 mg/min in adults, 5 mg/min in young animals. Second-generation agents may need 3–4 weeks (Bailey 1986).

### Birds

*Phytonadione (Vitamin K1) doses for birds*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Raptor / songbird secondary rodenticide poisoning | 2.5–5 mg/kg | IM | q24h × 2–4 weeks | — |

- Raptor / songbird secondary rodenticide poisoning: Papich 5e: birds 2.5–5 mg/kg q24h. Plumb’s p.976: 0.2–2.5 mg/kg IM as needed, usually 1–2 injections (Clubb 1986); 0.25–0.5 mL/kg IM of the 10 mg/mL product before surgery (McDonald 1989).

### Rabbits

*Phytonadione (Vitamin K1) doses for rabbits*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Rabbit rodenticide ingestion | 1.5–2.5 mg/kg | PO | q12h | 14 days (1st gen) to ≥30 days |

- Rabbit rodenticide ingestion: Plumb’s p.976: pocket pets are treated at the high end — loading dose 2.5–5 mg/kg PO, then 3–5 mg/kg/day PO divided twice daily (Merola 2002); injectable given PO at 5 mg/kg/day divided q8–12h with a fatty meal (Richardson 2002). SC injection can cause anaphylaxis; never IV. The calculator range (1.5–2.5 mg/kg q12h) corresponds to the 3–5 mg/kg/day maintenance dose.

### Small mammals

*Phytonadione (Vitamin K1) doses for small mammals*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Ferret / guinea pig rodenticide | 1.5–2.5 mg/kg | PO | q12h | 14 days (1st gen) to ≥30 days |

- Ferret / guinea pig rodenticide: Plumb’s p.976: rabbits, rodents and small mammals — loading 2.5–5 mg/kg PO, then 3–5 mg/kg/day divided twice daily (Merola 2002), or 5 mg/kg/day divided q8–12h (Richardson 2002); feed with a fatty meal. SC injection can cause anaphylaxis. The calculator range (1.5–2.5 mg/kg q12h) corresponds to 3–5 mg/kg/day divided twice daily.

## Contraindications

Hypersensitivity (rare anaphylaxis with IV — IV route is strongly discouraged, use SC if parenteral needed). Use with caution in severe hepatic dysfunction (impaired Vit K activation).

## Species-specific warnings

> **Caution:** Dogs: Second-gen rodenticide protocol: 3–4 weeks of Vit K1 PO with fatty meal. PT check 48–72 h after stopping.

> **Caution:** Birds: Secondary poisoning common in raptors / songbirds; rehab protocol 2.5–5 mg/kg IM daily × 3 weeks.

## Adverse effects

- Rare anaphylaxis with IV administration (do NOT use IV route)
- Local injection-site reaction (SC / IM)
- PO: rare GI upset

## Drug interactions

- Warfarin / anticoagulant rodenticides: Vit K1 IS the antidote
- Antibiotics suppressing gut flora: may reduce Vit K2 production but Vit K1 bypasses this
- Cholestyramine / orlistat: reduce Vit K1 absorption

## Pregnancy and lactation

Safe in pregnancy.

## Monitoring

- PT (prothrombin time) — baseline, then 48–72 h after stopping Vit K1 to confirm cessation is safe
- Clinical signs: bleeding, dyspnoea (pleural haemorrhage), pallor
- PCV / haemoglobin during active bleeding
- CBC weekly during 2–4 week course
- If PT remains elevated 48–72 h after stopping → CONTINUE Vit K1 another 2 weeks

## Toxicity and overdose

Wide safety margin orally. IV anaphylaxis: serious historical concern with Vit K1 IV — never use IV route. SC / PO are safe.

Management: Acute oral overdose: GI upset. Supportive care. No specific antidote needed.

## Clinical pearls

- GIVE WITH FATTY MEAL — bioavailability triples with fat in the stomach
- NEVER GIVE IV — anaphylaxis risk is real; use SC if parenteral needed
- Second-generation rodenticide (brodifacoum / bromadiolone — the most common in modern bait): minimum 3 weeks of treatment
- PT at 48–72 h after stopping is the cessation test — if elevated, restart for another 2 weeks
- Actively bleeding patient: SC Vit K1 + fresh-frozen plasma (gives immediate clotting factors) + supportive care
- Owner counselling — they must complete the full 3–4 weeks even when the dog appears fine. Treatment failure → death.
- Raptor / wildlife with secondary exposure: 2.5–5 mg/kg IM daily × 3 weeks is standard wildlife-rehab protocol

## Mechanism of action

Vitamin K1 (phylloquinone) is a required cofactor for hepatic gamma-carboxylation of coagulation factors II, VII, IX, X (and proteins C, S). Anticoagulant rodenticides inhibit vitamin K epoxide reductase, preventing recycling of Vit K — so the patient becomes "Vit K deficient" despite adequate dietary intake. Supplemental Vit K1 bypasses the inhibition by providing exogenous reduced Vit K. PO bioavailability is excellent WITH FATTY MEAL.

## Formulations and products

- Vitamin K1 capsule 5 mg
- Vitamin K1 capsule 25 mg
- Vitamin K1 capsule 50 mg
- Vitamin K1 injection 10 mg/mL

## Storage

Capsules: 15–25 °C dry. Injection: 15–25 °C protected from light. Multidose vial: discard 28 d after broaching.

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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## Frequently asked questions

### What is the dose of Phytonadione (Vitamin K1) for dogs?

Reference doses for Phytonadione (Vitamin K1) in dogs: 1.25–2.5 mg/kg PO q12h for 14 days (Anticoagulant rodenticide — first generation); 1.25–2.5 mg/kg PO q12h × 2–4 weeks for at least 4 weeks (≥30 days) (Anticoagulant rodenticide — second generation (brodifacoum)); 1.25–2.5 mg/kg SC first dose only, then PO (Acutely bleeding patient — SC for rapid effect). Confirm against the label and the patient before use.

### What is the dose of Phytonadione (Vitamin K1) for cats?

Reference doses for Phytonadione (Vitamin K1) in cats: 1.25–2.5 mg/kg PO q12h × 2–4 weeks (Anticoagulant rodenticide). Confirm against the label and the patient before use.

### What is the dose of Phytonadione (Vitamin K1) for cattle?

Reference doses for Phytonadione (Vitamin K1) in cattle: 1–1.5 mg/kg SC q24h for several days (Sweet clover poisoning (moulded dicoumarol)); 0.5–2.5 mg/kg IM repeat as needed (3–4 weeks for 2nd-generation) (Anticoagulant rodenticide toxicity). Confirm against the label and the patient before use.

### What is the withdrawal period for Phytonadione (Vitamin K1)?

Cattle, SC (Sweet clover poisoning (moulded dicoumarol)): Withdrawal NOT established — treat as extra-label; Cattle, IM (Anticoagulant rodenticide toxicity): Withdrawal NOT established — treat as extra-label; Goats, IM (Warfarin-type toxicity): Withdrawal NOT established — treat as extra-label; Sheep, IM (Warfarin-type toxicity): Withdrawal NOT established — treat as extra-label; Pigs, IM (Warfarin-type toxicity): Withdrawal NOT established — treat as extra-label. Follow the product label and national regulations where they differ.

### When should Phytonadione (Vitamin K1) not be used?

Hypersensitivity (rare anaphylaxis with IV — IV route is strongly discouraged, use SC if parenteral needed). Use with caution in severe hepatic dysfunction (impaired Vit K activation).

### What are the side effects of Phytonadione (Vitamin K1) in animals?

Rare anaphylaxis with IV administration (do NOT use IV route); Local injection-site reaction (SC / IM); PO: rare GI upset.

## Sources

- Plumb's Veterinary Drug Handbook
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.