VetSheet

華法林鈉

Warfarin Sodium

抗凝血劑 - 香豆素衍生物POIV狗貓馬

別名: Coumadin · Jantoven · Panwarfin · sodium warfarin · warfarinum natricum

由 VetSheet 獸醫團隊審訂更新於 2026年4月5日本內容以實證獸醫文獻為本

0.22 mg/kgPO· q12h
— 🐕

劑量為持牌獸醫專業人員的臨床參考。請務必對照最新藥品說明書及個別病患確認。

各物種劑量

🌎 NA — North America🌍 EU — Europe

狗

適應症劑量途徑頻次療程地區
Adjunctive maintenance therapy for venous thrombosis with or without pulmonary thromboembolism (PTE)0.22 mg/kgPOq12h—🌎 NA
Adjunctive therapy of thromboemboli0.22 mg/kgPOq12h—🌎 NA
Prophylactic use in patients with glomerular disease and severe proteinuria0.22 mg/kgPOonce daily—🌎 NA
  • Adjunctive maintenance therapy for venous thrombosis with or without pulmonary thromboembolism (PTE): Initially, then adjusted to achieve a PT prolongation of 1.25 to 1.5 times the pretreatment value.
  • Adjunctive therapy of thromboemboli: Target dosage to prolong PT by 1.25-1.5 times the pretreatment value.
  • Prophylactic use in patients with glomerular disease and severe proteinuria: Initially. Monitor PT and adjust dose so that PT is maintained at 1.5 times normal.

貓

適應症劑量途徑頻次療程地區
Adjunctive maintenance therapy for venous thrombosis with or without pulmonary thromboembolism (PTE)0.5 mg (total dose per cat)POonce daily—🌎 NA
Maintenance therapy for feline arterial thromboembolism0.06 to 0.09 mg/kg/dayPOonce daily—🌎 NA
Long-term thromboprophylaxis0.06-0.09 mg/kg per dayPOonce daily—🌎 NA
Adjunctive therapy of thromboembolism0.25-0.5 mg (total dose) per catPOonce daily—🌎 NA
Cardiogenic arterial thromboembolism0.25-0.5 mg total dose per catPOq24h—🌎 NA
  • Adjunctive maintenance therapy for venous thrombosis with or without pulmonary thromboembolism (PTE): Initially, then adjusted to achieve a PT prolongation of 1.25 to 1.5 times the pretreatment value.
  • Maintenance therapy for feline arterial thromboembolism: Heparinization is recommended during the first 5 to 7 days that warfarin is administered.
  • Long-term thromboprophylaxis: Initially. Tablets should be crushed and mixed well due to unequal drug distribution. Overlap heparin and warfarin therapy by at least 4-5 days.
  • Adjunctive therapy of thromboembolism: Initially. Adjust dosage to prolong PT to twice normal value, or INR to be between 2-3. Overlap therapy with heparin.
  • Cardiogenic arterial thromboembolism: Heparin (150-250 Units/kg SC q8h) should be administered concurrently during the first 4-6 days. Target PT range is 1.3-1.6 times baseline, or INR 2.0-3.0.

馬

適應症劑量途徑頻次療程地區
Adjunctive treatment of laminitis0.0198 mg/kgPOonce daily—🌎 NA
AnticoagulantInitially, 0.018 mg/kg PO once daily and increase dose by 20% every day until baseline PT is doubled. Final dose rates may be from 0.012 mg/kg to 0.57 mg/kg daily.POonce daily—🌎 NA
  • Adjunctive treatment of laminitis: Monitor OSPT (one-step prothrombin time) until prolonged 2-4 seconds beyond baseline.
  • Anticoagulant: ARCI UCGFS Class 5 Drug.

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概覽

華法林（Warfarin）是一種香豆素類抗凝血劑，主要用於貓、狗或馬的血栓性疾病的長期治療或預防。由於其治療指數狹窄、具有致命性出血的潛在風險，且需要頻繁且昂貴的凝血功能監測，其在獸醫學中的應用存在一定爭議，通常僅在其他抗凝血劑不可行時使用。

作用機制

Warfarin acts as an indirect anticoagulant by antagonizing Vitamin K.

  • It competitively inhibits the enzyme ​Vitamin K epoxide reductase (VKORC1)​.
  • This inhibition prevents the conversion of inactive Vitamin K epoxide back into its active form (Vitamin K hydroquinone).
  • Active Vitamin K is an essential cofactor for the γ-carboxylation (activation) of coagulation factors II, VII, IX, and X, as well as the endogenous anticoagulant proteins C and S.
  • ​Pathway:​ VKORC1 inhibition → Depletion of active Vitamin K → Production of inactive, undercarboxylated clotting factors (PIVKA) → Prolonged clotting times and anticoagulation.

安全性與警告

禁忌症

  • 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)
  • Visceral carcinomas

不良反應

  • 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
  • Death

注意事項

​Strict Monitoring Required:​ Warfarin has a narrow therapeutic index. Frequent monitoring of coagulation status (PT/INR) is mandatory to prevent fatal hemorrhage.

  • ​Teratogenicity:​ Warfarin is embryotoxic and causes congenital malformations. It is strictly contraindicated in pregnancy. Low-dose heparin is preferred if anticoagulation is required during pregnancy.
  • ​Nursing:​ Use with caution in nursing patients; prolonged prothrombin times have been reported in some breast-fed human infants.
  • ​Dietary Changes:​ Sudden changes in diet (especially foods high in Vitamin K) can alter the efficacy of warfarin.
  • ​Laboratory Interference:​ May cause falsely decreased theophylline values if using the Schack and Waxler ultraviolet method.

藥物相互作用

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).

監測

  • Prothrombin Time (PT) - Target usually 1.25 to 1.5x (or up to 2x) normal depending on protocol
  • International Normalized Ratio (INR) - Target usually 2.0 to 3.0 (Note: not fully validated for veterinary patients)
  • PIVKA (Proteins Induced by Vitamin K Antagonists) - May be more sensitive than PT
  • Platelet counts and hematocrit (PCV)
  • Occult blood in stool and urine
  • Physical observations for bleeding (mucous membranes, bruising, epistaxis)
  • Clinical efficacy (resolution/prevention of thromboembolism)

藥物動力學

半衰期

貓S-enantiomer: ~23-28 hours; R-enantiomer: ~11-18 hours

吸收

Rapidly and completely absorbed after oral administration in humans and cats.

分佈

Highly bound to plasma proteins (approximately 99% in humans, >96% in cats). Wide species variation exists; horses have a higher free (unbound) fraction than rats, sheep, or swine. Only the free fraction is active. Does not enter milk in humans.

代謝

Principally metabolized in the liver to inactive metabolites.

排除

Metabolites are excreted in urine and bile (then reabsorbed and excreted in the urine).

過量

Acute overdosages of warfarin may result in life-threatening hemorrhage.

  • ​Toxic Doses:​ In dogs and cats, single doses of 5-50 mg/kg have been associated with toxicity. Cumulative toxic doses are reported as 1-5 mg/kg for 5-15 days in dogs, and 1 mg/kg for 7 days in cats.
  • ​Lag Time:​ A lag time of 2-5 days may occur before clinical signs of toxicity manifest. Animals must be monitored closely during this period.
  • ​Treatment:​ If detected early, prevent absorption from the gut using standard decontamination protocols (emesis, activated charcoal). If clinical signs of bleeding are noted, treat with blood products (plasma/whole blood to replace active clotting factors) and ​Vitamin K1 (phytonadione)​.

可用產品

劑型

  • Oral tablets
  • Powder for injection (lyophilized)

獸醫用

  • None (ARCI Class 5 substance for racing)

人用標示

  • Warfarin Sodium Oral Tablets (scored): 1 mg, 2 mg, 2.5 mg, 3 mg, 4 mg, 5 mg, 6 mg, 7.5 mg & 10 mg (Coumadin, Jantoven, generic)
  • Warfarin Sodium Powder for Injection, lyophilized: 5.4 mg (2 mg/mL when reconstituted) preservative-free in 5 mg vials (Coumadin)

各地核准狀態

暫無法規資料: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU

儲存與穩定性

Tablets should be stored in tight, light-resistant containers at temperatures less than 40°C, preferably at room temperature. Powder for injection should be protected from light and used immediately after reconstituting.

飼主須知

請務必嚴格按照獸醫指示的劑量給藥，切勿自行更改劑量。若發現任何出血跡象（如牙齦蒼白、異常瘀傷、流鼻血、血尿、黑便或血便、突然虛弱），請立即聯繫獸醫。為防止外傷引發嚴重出血，服用此藥的寵物（尤其是貓咪）應盡量留在室內並避免劇烈活動。未經獸醫同意，請勿給寵物服用任何新藥物或保健品。

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