← Search & browse all drugs

warfarin

B01AA03

Forms & Strengths

Oral tablets: 1 mg, 2 mg, 2.5 mg, 3 mg, 4 mg, 5 mg, 6 mg, 7.5 mg, 10 mg

Adult Dosing

Initial dose: 2 mg to 5 mg orally once daily for the first 1 to 2 days
Maintenance dose: 2 mg to 10 mg orally once daily, adjusted based on target INR

Pediatric Dosing

Loading dose: 0.1 mg/kg orally once daily for 2 days (max 10 mg/day)
Maintenance dose: Titrated based on PT/INR, typically ranging from 0.05 mg/kg/day to 0.33 mg/kg/day

Indications

Prophylaxis and treatment of venous thrombosis and pulmonary embolism
Thromboembolic complications associated with atrial fibrillation and/or cardiac valve replacement

Mechanism of Action

Inhibits vitamin K epoxide reductase (VKORC1), preventing the regeneration of active vitamin K
Depletes functional vitamin K-dependent clotting factors II, VII, IX, and X, as well as proteins C and S

Contraindications

Hemorrhagic tendencies or blood dyscrasias
Recent or contemplated surgeries of the central nervous system or eye, or traumatic surgery resulting in large open surfaces
Bleeding tendencies associated with active ulceration or overt bleeding
Major regional or lumbar block anesthesia
Severe uncontrolled hypertension
Pregnancy (except in pregnant women with mechanical heart valves)

Adverse Reactions

Major or minor hemorrhage from any tissue or organ
Calciphylaxis
Warfarin-induced skin necrosis and gangrene
Nausea, vomiting, abdominal pain, diarrhea
Alopecia

Drug Interactions

CYP2C9, CYP1A2, and CYP3A4 inducers (e.g., rifampin, carbamazepine) decrease warfarin efficacy
CYP2C9 and CYP3A4 inhibitors (e.g., amiodarone, fluconazole, metronidazole) increase bleeding risk
Concomitant use of antiplatelets, NSAIDs, and SSRIs significantly increases bleeding risk
Vitamin K ingestion (dietary or supplements) decreases anticoagulant response

Curated Content: Needs Vetting Before Put to Clinical Use