What is the initial starting dose and INR (International Normalized Ratio) monitoring regimen for a patient with a history of Deep Vein Thrombosis (DVT) being transitioned from Lovenox (Enoxaparin) to warfarin (Coumadin)?

Initial Warfarin Dosing and INR Monitoring for Patients Transitioning from Lovenox to Warfarin

For a patient with recurrent DVT who was resistant to oral anticoagulants and is currently on Lovenox, the recommended initial warfarin dose is 5 mg daily with INR monitoring on day 4 and day 6, then twice weekly until stable.

Initial Warfarin Dosing

The initial dosing of warfarin must be individualized according to the patient's sensitivity to the drug as indicated by the INR. For most patients transitioning from Lovenox (enoxaparin) to warfarin:

• Start with 5 mg daily dosing rather than higher loading doses 1, 2
• Lower initial doses (2-4 mg) should be considered for:
  • Elderly patients
  • Debilitated patients
  • Patients with hepatic insufficiency
  • Patients with potential for greater than expected INR response 2

Higher loading doses (10 mg) are not recommended as they:

• Do not offer more rapid protection against thrombi formation
• May increase the incidence of hemorrhagic complications 2

Lovenox-Warfarin Overlap Period

When transitioning from Lovenox to warfarin:

1. Continue Lovenox at full therapeutic dose
2. Start warfarin at 5 mg daily concurrently
3. Continue both medications for at least 5 days and until the INR is ≥2.0 for at least 2 consecutive days 1
4. Only discontinue Lovenox after achieving therapeutic INR (2.0-3.0) for two consecutive days

INR Monitoring Schedule

The recommended INR monitoring schedule is:

• First INR check: Day 4 after starting warfarin 3
• Second INR check: Day 6 after starting warfarin 3
• Subsequent monitoring: Twice weekly until stable 1, 2
• Once stable: Weekly initially, then gradually decrease frequency to no less than once monthly 1

Target INR Range

• The target INR range for DVT treatment is 2.0-3.0 1

Dose Adjustment Considerations

When adjusting warfarin dosing:

• Most dose changes should alter the total weekly dose by 5-20% 4
• Single INR values slightly out of range may not require dose adjustment 4
• The average final maintenance dose for most patients is between 2-10 mg daily 2

Special Considerations for This Patient

Since this patient has a history of resistance to oral anticoagulants (including direct oral anticoagulants):

1. Monitor INR more frequently initially (twice weekly) until stability is demonstrated
2. Consider a longer overlap period between Lovenox and warfarin to ensure adequate anticoagulation
3. Be prepared to adjust dosing more aggressively if therapeutic INR is not achieved with standard dosing

Common Pitfalls to Avoid

• Avoid high loading doses: Starting with 10 mg can lead to excessive anticoagulation and increased bleeding risk 2, 4
• Don't discontinue Lovenox too early: Continue until INR is therapeutic for at least 2 consecutive days 1
• Don't monitor INR too infrequently: More frequent monitoring is needed during initiation phase 2
• Don't make large dose adjustments: Small, incremental changes (5-20% of weekly dose) are safer 4
• Don't ignore patient-specific factors: Age, comorbidities, and concomitant medications can affect warfarin response 2

This approach balances the need for effective anticoagulation with safety considerations in a patient with recurrent DVT who has demonstrated resistance to oral anticoagulants.