What is the appropriate heparin dosing for a patient with bilateral extensive deep vein thrombosis who is currently taking apixaban (Eliquis)?

Discontinue Eliquis and Initiate Weight-Based Unfractionated Heparin Immediately

For a patient with bilateral extensive DVT already on apixaban (Eliquis), you must stop the apixaban and start unfractionated heparin (UFH) at an 80 units/kg IV bolus followed by 18 units/kg/hour continuous infusion, with dose adjustments based on aPTT monitoring to maintain a ratio of 1.5-2.5 times baseline. 1, 2, 3

Why Switch from Eliquis to Heparin?

The patient is experiencing breakthrough thrombosis while on therapeutic anticoagulation with apixaban. This represents treatment failure and requires immediate escalation to parenteral anticoagulation with closer monitoring capability.

• Eliquis has failed to prevent this extensive bilateral DVT
• UFH provides immediate, titratable anticoagulation with rapid onset and the ability to monitor therapeutic levels through aPTT
• The extensive, bilateral nature of the thrombosis demands aggressive initial management with a monitored parenteral agent 1, 2

Specific UFH Dosing Protocol

Initial Dosing:

• IV bolus: 80 units/kg (do not exceed 10,000 units in practice)
• Continuous infusion: 18 units/kg/hour 1, 2, 3

Monitoring and Adjustment:

• Check aPTT 4-6 hours after bolus and after each dose adjustment
• Target aPTT: 1.5-2.5 times the patient's baseline (or laboratory control) 1, 2
• Achieving therapeutic aPTT within 24 hours is critical - failure to do so is associated with significantly higher recurrence rates (up to 25%) 1

Dose Adjustment Nomogram:

Use a weight-based nomogram validated at your institution. The evidence strongly supports that weight-based dosing achieves therapeutic levels faster and reduces recurrence compared to fixed-dose regimens 1.

Critical Management Considerations

Why Not Continue Eliquis at Higher Dose?

• No evidence supports dose escalation of apixaban beyond standard therapeutic dosing for breakthrough thrombosis
• The FDA-approved treatment dose is already 10 mg twice daily for 7 days, then 5 mg twice daily 4
• Guidelines specifically suggest switching to LMWH (or by extension, UFH) for breakthrough VTE on DOACs 5

Why UFH Over LMWH?

For bilateral extensive DVT, UFH offers advantages:

• Immediate reversibility if bleeding complications arise
• Real-time monitoring of anticoagulant effect through aPTT
• Dose titration based on response
• Preferred in severe renal dysfunction (CrCl <30 mL/min) as it's hepatically cleared 3

However, if the patient has normal renal function and you prefer subcutaneous administration, LMWH is an acceptable alternative:

• Enoxaparin: 1 mg/kg subcutaneously every 12 hours 6, 2
• Dalteparin: 200 units/kg subcutaneously once daily 6

Duration and Transition Planning

Overlap with warfarin (or restart of a DOAC if appropriate after investigation):

• Start warfarin simultaneously with heparin
• Continue UFH for minimum 5 days AND until INR ≥2.0 for at least 24 hours 2
• Do NOT restart apixaban without investigating why it failed (consider checking anti-Xa levels if available, assess compliance, evaluate for drug interactions, consider underlying hypercoagulable state)

Investigation of Treatment Failure

Before restarting any oral anticoagulant, investigate:

• Medication adherence - was the patient actually taking apixaban as prescribed?
• Drug interactions - particularly P-glycoprotein or CYP3A4 inducers that reduce apixaban levels 4
• Underlying hypercoagulable state - consider thrombophilia workup, occult malignancy screening
• Adequate initial dosing - was the patient on the correct treatment dose (10 mg BID × 7 days, then 5 mg BID)?

Special Populations

If creatinine clearance <30 mL/min:

• UFH is strongly preferred over LMWH 3
• No dose adjustment needed for UFH

If active cancer:

• After acute phase with UFH, transition to LMWH rather than warfarin or DOACs for long-term management 6, 7
• Dalteparin 200 units/kg daily × 1 month, then 150 units/kg daily 6

Monitoring for Heparin-Induced Thrombocytopenia (HIT)

• Check baseline platelet count
• Monitor platelets every 2-3 days from day 4 to day 14 of heparin therapy 2, 8
• If platelets drop ≥50% from baseline, stop heparin immediately and consider alternative anticoagulation (argatroban, bivalirudin, or fondaparinux) 8

Common Pitfalls to Avoid

1. Do not continue apixaban - this represents treatment failure
2. Do not use prophylactic-dose anticoagulation - this is acute, extensive thrombosis requiring full therapeutic dosing
3. Do not delay achieving therapeutic anticoagulation - subtherapeutic anticoagulation in the first 24 hours dramatically increases recurrence risk 1
4. Do not restart apixaban without investigation - determine why it failed before considering any DOAC
5. Do not forget to overlap adequately when transitioning to warfarin (minimum 5 days AND INR ≥2.0 × 24 hours)