Transitioning from Heparin Infusion to Enoxaparin
Stop the heparin infusion and start enoxaparin immediately without any waiting period or overlap—there is no need to check aPTT before initiating enoxaparin. 1
Dosing Protocol
Standard Therapeutic Dosing
- Enoxaparin 1 mg/kg subcutaneously every 12 hours is the preferred regimen for most patients transitioning from therapeutic heparin 2
- Alternative: 1.5 mg/kg subcutaneously once daily is equally effective and may improve compliance 3, 4, 5
Age-Specific Adjustments
- Age <75 years: Use standard dosing as above 2
- Age ≥75 years (ACS patients): Reduce to 0.75 mg/kg every 12 hours with no initial IV bolus 2
Renal Function Considerations
Severe renal impairment (CrCl <30 mL/min) requires mandatory dose reduction to prevent drug accumulation and bleeding risk 2, 1:
- Reduce therapeutic dose to 1 mg/kg once daily (instead of twice daily)
- This is critical because enoxaparin is renally cleared 2, 1
For patients with CrCl ≥30 mL/min, no dose adjustment is necessary 2
Timing of Transition
Discontinue the heparin infusion and administer the first enoxaparin dose immediately—no washout period or bridging is required 1. The guidelines do not specify waiting for aPTT normalization before starting enoxaparin, as enoxaparin does not require aPTT monitoring 2.
Safety Monitoring
Platelet Count Requirements
- Minimum platelet count ≥50,000/mm³ for prophylactic dosing 1
- Minimum platelet count ≥100,000/mm³ for therapeutic dosing 1
- Monitor platelets every 2-3 days for the first 14 days, then every 2 weeks to detect heparin-induced thrombocytopenia 1
Bleeding Risk Assessment
- Obtain baseline hemoglobin/hematocrit before transition 2
- Active major bleeding is an absolute contraindication to enoxaparin 1
- History of heparin-induced thrombocytopenia is an absolute contraindication 1
Duration of Therapy
- Minimum 48 hours of anticoagulation required 2
- Continue for the duration of index hospitalization, up to 8 days or until revascularization if planned 2
- For venous thromboembolism: overlap with warfarin for minimum 5-7 days and continue enoxaparin until INR is therapeutic (2.0-3.0) for 2 consecutive days 2, 1
- Cancer patients require at least 3 months or as long as cancer is active 1
Common Pitfalls to Avoid
Do not wait for aPTT to normalize before starting enoxaparin—this creates an unnecessary gap in anticoagulation and increases thrombotic risk 1. The highly variable dose-response of unfractionated heparin means only 29% of patients maintain therapeutic aPTT on consecutive measurements, and 54% experience prolonged interruptions in therapy 6.
Do not use aPTT monitoring with enoxaparin—it does not correlate with anti-Xa activity and provides no useful clinical information 4, 5.
Do not forget renal dose adjustment—failure to reduce dosing in severe renal impairment (CrCl <30 mL/min) significantly increases major bleeding risk 2.
Do not administer enoxaparin within 8-12 hours of epidural catheter removal if neuraxial anesthesia was used 1.
Advantages of This Transition
Enoxaparin offers superior pharmacokinetics compared to unfractionated heparin: more predictable anticoagulation without monitoring, subcutaneous administration, potential for outpatient management, and reduced hospital stay by an average of 4 days 4, 5. Studies demonstrate at least equivalent efficacy with similar or lower bleeding rates compared to continuous heparin infusion 3, 4, 5.