Dalteparin Sodium Anti-Xa Units
A 5,000-unit vial of dalteparin sodium contains 5,000 anti-Xa international units (IU). The units of dalteparin are directly expressed as anti-Xa international units, meaning there is a 1:1 correspondence 1, 2.
Key Clinical Context
Dalteparin is a low-molecular-weight heparin with a mean molecular weight of approximately 5,000 daltons 3. The dosing is standardized based on anti-Xa activity:
- Prophylactic dosing: 5,000 anti-Xa IU once daily is the standard dose for VTE prophylaxis in hospitalized medical patients, surgical patients, and many outpatients 1
- Therapeutic dosing: Ranges from 100 IU/kg every 12 hours to 200 IU/kg once daily for treatment of established VTE 1
Important Clinical Considerations
Target anti-Xa levels vary by indication:
Monitoring is generally not required for standard prophylactic dosing, but anti-Xa monitoring should be considered in specific populations 6:
- Renal insufficiency (creatinine clearance <60 mL/min)
- Morbid obesity (BMI >50)
- Pregnancy
- Critically ill patients where wide interindividual variation in absorption and clearance occurs 4
When monitoring is performed, samples must be drawn 3-5 hours after subcutaneous injection and after steady state (at least 3 doses) to be clinically meaningful 6. Non-compliance with proper sampling timing is common (48% in one study) and leads to unjustified dose adjustments 6.
Dose adjustments may be needed in high-risk populations. In trauma patients, 51% had subtherapeutic anti-Xa levels with once-daily 5,000 IU dosing, and switching to twice-daily dosing reduced VTE rates 7. Younger age and higher weight predict lower anti-Xa levels 7.