Is it appropriate to take enoxaparin (low molecular weight heparin) and Coumadin (warfarin) together when transitioning to Coumadin (warfarin)?

Concurrent Use of Enoxaparin and Warfarin During Transition to Warfarin Therapy

Yes, it is appropriate and recommended to take enoxaparin and warfarin (Coumadin) together during the transition period to warfarin therapy. 1 This overlapping approach ensures continuous anticoagulation while waiting for warfarin to reach therapeutic effect.

Rationale for Concurrent Therapy

When transitioning to warfarin, parenteral anticoagulation with enoxaparin should overlap with warfarin for specific reasons:

• Warfarin has a delayed onset of action (typically 5-7 days to reach therapeutic effect)
• Immediate discontinuation of parenteral anticoagulation would leave the patient at risk for thrombosis
• The FDA drug label for warfarin specifically states: "To ensure continuous anticoagulation, it is advisable to continue full dose heparin therapy and that warfarin sodium tablets therapy be overlapped with heparin for 4 to 5 days, until warfarin sodium tablets have produced the desired therapeutic response as determined by PT/INR" 1

Recommended Protocol for Transition

1. Initial Phase:

   • Begin warfarin while continuing full-dose enoxaparin
   • Enoxaparin dosing: 1 mg/kg subcutaneously every 12 hours or 1.5 mg/kg once daily 2
   • Start warfarin at appropriate dose (typically 5-10 mg, with lower doses for elderly or hospitalized patients) 2

2. Monitoring Phase:

   • Monitor INR daily until stable in therapeutic range (typically 2.0-3.0) 1
   • Continue both medications during this phase

3. Discontinuation of Enoxaparin:

   • Continue enoxaparin for a minimum of 5 days AND
   • Continue until INR is in therapeutic range (2.0-3.0) for at least 24 hours 2
   • Then discontinue enoxaparin while continuing warfarin alone

Evidence Supporting This Approach

Multiple guidelines support this approach:

• The American College of Chest Physicians guidelines recommend LMWH (like enoxaparin) should overlap with warfarin for a minimum of 5 days and until the INR is ≥2.0 for at least 24 hours 2
• The European Society of Cardiology guidelines state: "Parenteral heparin should overlap with the initiation of a vitamin K antagonist" 2
• The FDA-approved warfarin label explicitly recommends overlapping therapy 1

Important Considerations

• Avoid switching between different anticoagulants: Do not switch between unfractionated heparin and LMWH due to increased bleeding risk 2
• INR monitoring timing: When a patient is receiving both heparin and warfarin, blood for PT/INR determination should be drawn at least 4-5 hours after IV heparin doses or 24 hours after subcutaneous heparin injections 1
• Duration of overlap: Typically 4-5 days, but may be longer if INR does not reach therapeutic range 1
• Renal function: Adjust enoxaparin dose in patients with impaired renal function (CrCl <30 mL/min) 2

Common Pitfalls to Avoid

1. Premature discontinuation of enoxaparin: Stopping enoxaparin before warfarin reaches therapeutic levels can leave patients unprotected
2. Inadequate monitoring: Failing to check INR daily during the transition period
3. Improper timing of blood draws: Drawing blood for INR testing too soon after enoxaparin administration can affect results
4. Failure to adjust for renal function: Not reducing enoxaparin dose in patients with renal impairment

This approach of overlapping enoxaparin with warfarin has been shown to be both safe and effective in ensuring continuous anticoagulation during the transition period, which is critical for preventing thrombotic events while minimizing bleeding risk.