Warfarin

Aka: Warfarin, Coumadin

1. See Also
   1. Coumadin Drug Interactions
   2. Coumadin Protocol
   3. Coumadin Protocol for the Perioperative Period
   4. Heparin
2. Mechanism
   1. Inhibits Vitamin K participation in factor synthesis
   2. Vitamin K dependent coagulation proteins
      1. Procoagulant Activity
         1. Factor II (72 hour half life)
         2. Factor VII (8 hour half life)
         3. Factor IX (24 hour half life)
         4. Factor X (39 hour half life)
      2. Anticoagulant Activity
         1. Protein C (14 hour half life)
         2. Protein S (42 hour half life)
   3. Coumadin has an initial paradoxical procoagulant effect
      1. Anticoagulant factors are depleted first
      2. Concurrently administer Heparin for first 4-5 days
3. Monitoring: Target INR
   1. INR between 2.0 and 3.0
      1. Most conditions
      2. Hip replacement or ORIF Fracture (for 28-35 days)
      3. Elective total knee arthroplasty (for 10 days)
      4. Atrial Fibrillation
         1. High CVA risk
         2. Persistent, paroxysmal Atrial Fibrillation, flutter
         3. Cardioversion (3 weeks before, 4 weeks after)
      5. Deep Vein Thrombosis
         1. First episode with reversible risks: 3 months
         2. First episode and idiopathic: 6-12 months
         3. Cancer: LMWH x3-6 months, then Warfarin longterm
         4. Antiphospholipid Antibody: 12 months or longterm
         5. Two Thrombophilias: 12 months or longterm
         6. Clotting disorder related: 6-12 months or longterm
         7. Two or more episodes: Longterm
   2. INR between 2.5 and 3.5
      1. Mechanical Heart Valves
         1. Ball and cage valve
         2. Comorbid Atrial Fibrillation, CHF, MI, LAE
         3. Mitral valve replacement
      2. Antiphospholipid Syndrome (Lupus Anticoagulant)
      3. Prevent recurrent Myocardial Infarction
         1. Indicated in Aspirin intolerant patient
4. Dosing Protocol
   1. See Coumadin Protocol