【藥品性質提示】 根據 2019 AGS Beers Criteria，本藥品為【潛在不適當用藥 (PIM)】，不建議老年人併用以下藥品使用，會增加出血風險：Amiodarone、Ciprofloxacin、Macrolides、TMP/SMX、NSAID。 #高警訊藥品

抗凝血口服
Myocardial infarction: Adjunct to reduce risk of systemic embolism (eg, recurrent myocardial infarction, stroke) after myocardial infarction.
Thromboembolic complications: Prophylaxis and treatment of thromboembolic disorders (eg, venous, pulmonary) and embolic complications arising from atrial fibrillation or cardiac valve replacement.

Anticoagulant, Vitamin K Antagonist
Hepatic synthesis of coagulation factors II, VII, IX, and X, as well as proteins C and S, requires the presence of vitamin K. These clotting factors are biologically activated by the addition of carboxyl groups to key glutamic acid residues within the proteins' structure. Warfarin competitively inhibits the subunit 1 of the multi-unit VKOR complex, thus depleting functional vitamin K reserves and hence reduces synthesis of active clotting factors.

1. Absorption: Completely absorbed orally
2. Protein binding: approximately 99%
3. Metabolism: CYP450 CYP2C9, CYP2C19, CYP2C8, CYP2C18, CYP1A2, CYP3A4 and reductases
4. Excretion: <2% is excreted unchanged in urine
5. Elimination Half Life: approximately 1 week

1. Hypersensitivity to warfarin or any component of the formulation
2. Hemorrhagic tendencies (eg, active GI ulceration; active bleeding; cerebral aneurysm; spinal puncture and other diagnostic or therapeutic procedures)
3. Recent or potential surgery of the eye or CNS
4. Threatened abortion, pregnancy (except in women with mechanical heart valves at high risk for thromboembolism)

X; Use is contraindicated during pregnancy except in patients with mechanical heart valves who are at high risk for thromboembolism.

Warfarin is considered compatible with breastfeeding.

Hemorrhage, purple-toe syndrome, systemic cholesterol micro-embolism, vasculitis, chills, pruritus, abdominal pain, diarrhea, flatulence, nausea, vomiting, hepatitis, anaphylaxis, acute renal failure, tracheobronchial calcification

Dosage:
1. Initial: 5 mg once daily; at least 4-6 days of warfarin therapy are required before full therapeutic effect is achieved.
2. Maintenance: 2 to 10 mg once daily
Monitor:
Regular monitoring of INR should be performed on all treated patients.

1. eGFR <60 mL/minute/1.73 m2: ~10% to 20% lower doses
2.ESRD: require ~20% lower doses
3. Intermittent hemodialysis, Peritoneal dialysis: Unlikely to be dialyzed
4. CRRT, PIRRT: Avoid use

1. There are no dosage adjustments provided in the manufacturer's labeling. However, the response to oral anticoagulants may be markedly enhanced in obstructive jaundice, hepatitis, and cirrhosis.
2. INR should be closely monitored.