What is the therapeutic dose of fondaparinux (a low molecular weight heparin) for anticoagulation?

Therapeutic Dosing of Fondaparinux for Anticoagulation

For therapeutic anticoagulation, fondaparinux should be dosed based on body weight: 5 mg once daily for patients <50 kg, 7.5 mg once daily for patients 50-100 kg, and 10 mg once daily for patients >100 kg. 1, 2

Weight-Based Dosing Algorithm

Fondaparinux is administered as a once-daily subcutaneous injection with the following weight-based dosing:

• <50 kg: 5 mg once daily
• 50-100 kg: 7.5 mg once daily
• >100 kg: 10 mg once daily 1, 2

Pharmacokinetics and Administration

Fondaparinux has predictable pharmacokinetic properties that make it suitable for fixed dosing:

• Rapidly and completely absorbed after subcutaneous injection
• Terminal half-life of 17 hours in young subjects and 21 hours in elderly patients
• Steady state reached after 3-4 doses
• Peak plasma concentration occurs approximately 3 hours post-dose 1
• Excreted unchanged in the urine 1

Monitoring

• Routine coagulation monitoring is not recommended for most patients 1
• If monitoring is clinically necessary (e.g., extremes of body weight, renal dysfunction):
  • Use fondaparinux-specific anti-Xa assays
  • Expected peak steady-state plasma concentration for therapeutic dosing: 1.20-1.26 mg/L at 3 hours post-dose 1
  • Target anti-Xa activity range: 0.5-1.0 mg/L 1

Special Populations

Renal Impairment

• Contraindicated in severe renal insufficiency (CrCl <30 mL/min) 3, 4
• For moderate renal insufficiency (CrCl 30-50 mL/min) requiring thromboprophylaxis:
  • Reduce dose by 50% or consider alternative anticoagulants 1

Pediatric Patients

• Starting dose of 0.1 mg/kg once daily is recommended for children aged 1-17 years
• Target peak concentration: 0.5-1.0 mg/L measured 4 hours after administration 1

Duration of Treatment

• For DVT/PE treatment: Minimum 5 days and until therapeutic oral anticoagulant effect is established (INR 2-3)
• Typical duration: 5-9 days (up to 26 days in clinical trials) 2
• Initiate warfarin as soon as possible, usually within 72 hours 2

Important Safety Considerations

• No antidote exists for fondaparinux 1
• Does not bind to protamine sulfate (the antidote for heparin)
• For uncontrollable bleeding, recombinant factor VIIa may be effective 1
• The anticoagulant effect may persist for 2-4 days after discontinuation in patients with normal renal function 1

Advantages in Special Situations

• Low affinity for platelet factor 4 (PF4) and does not cross-react with HIT antibodies
• May be suitable for patients with history of heparin-induced thrombocytopenia (HIT) 1

Fondaparinux provides a predictable anticoagulant response with once-daily dosing and minimal need for monitoring in most patients, making it a convenient option for therapeutic anticoagulation when appropriate for the clinical situation.