What are the equivalent doses of Low Molecular Weight Heparin (LMWH), warfarin, apixaban, rivaroxaban, and dabigatran?

Equivalent Dosing of Anticoagulants

There is no direct "equivalent dose" conversion between these anticoagulants because they have fundamentally different mechanisms of action, pharmacokinetics, and clinical indications—each must be dosed according to its specific FDA-approved regimen for the clinical scenario (VTE treatment, atrial fibrillation, or thromboprophylaxis). 1

Standard Therapeutic Dosing by Indication

For Atrial Fibrillation (Stroke Prevention)

Warfarin:

• Target INR 2.0-3.0, typically starting at 5 mg daily (or 2.5 mg if liver disease or drug interactions present) 1

Dabigatran:

• 150 mg twice daily (standard dose) 1
• 110 mg twice daily available in some countries (not U.S.) 1
• Reduce to 75 mg twice daily if CrCl 15-30 mL/min (U.S. only) 1

Apixaban:

• 5 mg twice daily (standard dose) 1
• Reduce to 2.5 mg twice daily if patient has two or more of: age ≥80 years, weight ≤60 kg, serum creatinine ≥1.5 mg/dL 1

Rivaroxaban:

• 20 mg once daily with food (standard dose) 1
• Reduce to 15 mg once daily if CrCl 30-50 mL/min 1

Edoxaban:

• 60 mg once daily (standard dose) 1
• Reduce to 30 mg once daily if: CrCl 30-50 mL/min, weight ≤60 kg, or concomitant P-glycoprotein inhibitor 1

For VTE Treatment (DVT/PE)

Low Molecular Weight Heparin (LMWH):

• Enoxaparin: 1 mg/kg subcutaneously every 12 hours (or 1.5 mg/kg once daily after first month in some patients) 1, 2
• Dalteparin: 200 units/kg subcutaneously once daily for 30 days, then 150 units/kg once daily 1

Warfarin:

• Start at 5 mg daily, adjust to INR 2.0-3.0 1
• Requires initial LMWH overlap for at least 5 days until INR ≥2.0 for 2 consecutive days 1

Apixaban:

• 10 mg twice daily for 7 days, then 5 mg twice daily 1
• No parenteral lead-in required 1

Rivaroxaban:

• 15 mg twice daily for 21 days, then 20 mg once daily with food 1
• No parenteral lead-in required 1

Dabigatran:

• Requires initial LMWH or UFH for at least 5 days, then 150 mg twice daily 1

Edoxaban:

• Requires initial LMWH or UFH for at least 5 days, then 60 mg once daily 1
• Reduce to 30 mg once daily if: CrCl 30-50 mL/min, weight ≤60 kg, or concomitant P-glycoprotein inhibitor 1

Key Pharmacokinetic Differences (Not Dose Equivalents)

These parameters explain why direct conversion is impossible:

• Dabigatran: 3-7% bioavailability, 80% renal clearance, 50-60% dialyzable 1
• Apixaban: 50% bioavailability, 27% renal clearance, 14% dialyzable 1
• Rivaroxaban: 66-100% bioavailability (with food), 35% renal clearance, not significantly dialyzable 1
• Edoxaban: 62% bioavailability, 50% renal clearance, partially dialyzable 1
• Warfarin: Unpredictable dose-response, extensive drug-food interactions, requires monitoring 1, 3
• LMWH: Not orally bioavailable, weight-based dosing, 100% subcutaneous administration 3, 4

Critical Clinical Considerations

Renal Function Mandates Dose Adjustment:

• All DOACs require dose reduction or avoidance in severe renal impairment (CrCl <30 mL/min), whereas warfarin remains an option 1
• For dialysis patients, warfarin or apixaban (with caution) are the only reasonable options; other DOACs are contraindicated 1

Cancer-Associated VTE:

• LMWH (enoxaparin or dalteparin) is preferred over warfarin due to superior efficacy 1, 2
• DOACs are now acceptable alternatives, but apixaban is preferred over rivaroxaban/edoxaban for patients with gastric or gastroesophageal lesions due to lower bleeding risk 1

Transitioning Between Agents:

• When switching from warfarin to LMWH: discontinue warfarin and start enoxaparin when INR <2.0 2
• When switching from warfarin to DOACs: start DOAC when INR <2.0-2.5 (agent-specific) 1
• When switching from LMWH to warfarin: overlap for at least 5 days until therapeutic INR achieved 1
• Dabigatran and edoxaban require parenteral anticoagulation first; do not start concurrently with warfarin 1

Common Pitfalls to Avoid

• Do not attempt mathematical dose conversion between these agents—each has distinct pharmacology requiring protocol-specific dosing 1, 3
• Do not use rivaroxaban or dabigatran in dialysis patients—they accumulate dangerously 1
• Do not forget food requirements: rivaroxaban 15-20 mg doses must be taken with food for adequate absorption 1
• Do not overlook P-glycoprotein interactions: all DOACs are affected by inhibitors (ketoconazole, verapamil, amiodarone, dronedarone) and inducers (rifampin, phenytoin, St. John's wort) 1
• Do not use LMWH anti-FXa assays to quantify DOAC levels—they can only exclude clinically relevant concentrations, not measure them accurately 5