Warfarin Sodium
Also known as: Coumadin, Jantoven, Panwarfin
> **Critical Warning:** Warfarin is a potent blood thinner. Strict adherence to the prescribed dosing schedule is absolutely essential. Do not skip doses or give extra doses without consulting your veterinarian. * **Watch for Bleeding:** Immediately report any signs of bleeding to your veterinarian. This includes pale gums, unusual bruising, nosebleeds, blood in the urine or stool (which may look black and tarry), vomiting blood, coughing up blood, or sudden weakness/lethargy. * **Prevent Trauma:** Keep pets (especially cats) indoors and restrict rough play to minimize the risk of traumatic injury, which could lead to severe bleeding. * **Medication Interactions:** Do not give your pet any new medications, supplements, or over-the-counter drugs (especially aspirin or other pain relievers) without checking with your veterinarian, as many drugs interact dangerously with warfarin. * **Diet:** Keep your pet's diet consistent, as sudden changes in food (especially those containing Vitamin K) can alter how the drug works.
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 maintenance therapy for venous thrombosis with or without pulmonary thromboembolism (PTE)
- Maintenance therapy for feline arterial thromboembolism
- Long-term thromboprophylaxis
- Adjunctive therapy of thromboembolism
- Cardiogenic arterial thromboembolism
- Adjunctive treatment of laminitis
- Anticoagulant
- Adjunctive maintenance therapy for venous thrombosis with or without pulmonary thromboembolism (PTE)
- Adjunctive therapy of thromboemboli
- Prophylactic use in patients with glomerular disease and severe proteinuria
How it is given
Possible side effects
- Dose-related hemorrhage (primary adverse effect)
- Anemia
- Thrombocytopenia
- Weakness
- Hematomas and ecchymoses
- Epistaxis (nosebleeds)
- Hematemesis (vomiting blood)
- Hematuria (blood in urine)
- Melena (dark, tarry stools)
- Hematochezia (fresh blood in stools)
- Hemarthrosis (bleeding into joints)
- Hemothorax
- Intracranial hemorrhage
- Pericardial hemorrhage
Cautions & contraindications
- Preexistent hemorrhagic tendencies or diseases
- Patients undergoing or contemplating eye or CNS surgery
- Major regional lumbar block anesthesia
- Surgery of large, open surfaces
- Active bleeding from the GI, respiratory, or GU tract
- Aneurysm
- Acute nephritis
- Cerebrovascular hemorrhage
- Blood dyscrasias
- Uncontrolled or malignant hypertension
- Hepatic insufficiency
- Pericardial effusion
- Pregnancy (Teratogenic - FDA Category X / Papich Class D)
Drug interactions
- Acetaminophen, NSAIDs, Salicylates: May increase anticoagulant response (via protein displacement or platelet inhibition); increases bleeding risk.
- Fluoroquinolones, Macrolides (Azithromycin, Erythromycin), Chloramphenicol, Sulfonamides, Co-trimoxazole: May increase anticoagulant response (often via inhibition of hepatic metabolism).
- Cimetidine, Cisapride, Fluoxetine, Metronidazole, Sertraline: May increase anticoagulant response.
- Amiodarone, Allopurinol, Danazol, Diazoxide, Ethacrynic acid, Pentoxifylline, Propylthiouracil, Quinidine, Zafirlukast: May increase anticoagulant response.
- Anabolic Steroids, Thyroid Medications: May increase anticoagulant response.
- Heparin: Increases anticoagulant response; often used concurrently during the initial overlap phase but requires careful monitoring.
- Barbiturates (e.g., Phenobarbital), Rifampin, Griseofulvin: May decrease anticoagulant response (via induction of hepatic metabolizing enzymes).
- Corticosteroids, Estrogens, Mercaptopurine, Spironolactone, Sucralfate: May decrease anticoagulant response.
- Vitamin K: Directly antagonizes warfarin, decreasing its anticoagulant response (used as an antidote for overdose).
Frequently asked questions
What is Warfarin Sodium used for in pets?
> **Critical Warning:** Warfarin is a potent blood thinner. Strict adherence to the prescribed dosing schedule is absolutely essential. Do not skip doses or give extra doses without consulting your veterinarian. * **Watch for Bleeding:** Immediately report any signs of bleeding to your veterinarian. This includes pale gums, unusual bruising, nosebleeds, blood in the urine or stool (which may look black and tarry), vomiting blood, coughing up blood, or sudden weakness/lethargy. * **Prevent Trauma:** Keep pets (especially cats) indoors and restrict rough play to minimize the risk of traumatic injury, which could lead to severe bleeding. * **Medication Interactions:** Do not give your pet any new medications, supplements, or over-the-counter drugs (especially aspirin or other pain relievers) without checking with your veterinarian, as many drugs interact dangerously with warfarin. * **Diet:** Keep your pet's diet consistent, as sudden changes in food (especially those containing Vitamin K) can alter how the drug works.
Is Warfarin Sodium 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.
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