What is the recommended dose of Fragmin (Dalteparin) for prophylaxis against deep vein thrombosis?

ASRA Recommendations for Fragmin (Dalteparin) and Neuraxial Anesthesia

For prophylactic dosing of Fragmin (dalteparin), wait at least 12 hours after the last dose before performing neuraxial anesthesia or removing an epidural catheter, and delay the next dose for at least 4 hours after catheter removal or neuraxial block. 1

Timing Guidelines for Neuraxial Procedures

Before Neuraxial Anesthesia or Catheter Removal

• Prophylactic doses (2,500-5,000 units once daily): Wait minimum 12 hours after last dose before performing spinal/epidural anesthesia or removing catheter 1
• This timing applies to standard prophylactic regimens used for DVT prevention 2

After Neuraxial Anesthesia or Catheter Removal

• For prophylactic doses (once daily regimen): May start as early as 4 hours after catheter removal, but not earlier than 12 hours after the neuraxial block was performed 1
• For intermediate doses (twice daily regimen): Start 4 hours after catheter removal, but not earlier than 24 hours after the neuraxial block was performed 1

Standard Prophylactic Dosing Regimens

General Surgical Prophylaxis

• Abdominal surgery (standard risk): Dalteparin 2,500 units subcutaneously once daily, starting 1-2 hours before surgery and continuing 5-10 days postoperatively 2
• Abdominal surgery with malignancy (high risk): Dalteparin 5,000 units subcutaneously once daily, which is significantly more effective than 2,500 units in cancer patients (9.3% vs 15.1% DVT rate, p=0.001) 2

Orthopedic Surgery Prophylaxis

• Hip replacement surgery: Dalteparin 2,500-5,000 units subcutaneously once daily, with first dose given either immediately before surgery or 4-8 hours after surgery 2, 3
• Preoperative dosing (immediately before surgery) provides superior efficacy compared to warfarin (10.7% vs 24.0% DVT rate, p<0.001) but carries increased risk of major bleeding at surgical site 3
• Postoperative dosing (4-8 hours after surgery) provides similar efficacy to preoperative dosing without significantly increased bleeding 3

Medical Patients

• Acutely ill medical patients with restricted mobility: Dalteparin 5,000 units subcutaneously once daily for 14 days 2
• This regimen significantly reduces DVT incidence through Day 21 with sustained effect through Day 90 2

Special Population Considerations

Renal Insufficiency

• Severe renal impairment (CrCl <30 mL/min): Dalteparin 5,000 units once daily does NOT cause bioaccumulation and maintains trough anti-Xa levels <0.10 IU/mL in critically ill patients 4
• Unlike enoxaparin, dalteparin appears safer in severe renal insufficiency, with no excessive anticoagulant effect detected after median 7 days of treatment 4
• Mean anti-Xa activity remains similar between patients with severe renal impairment (mean CrCl 26 mL/min) and those with normal renal function 5

Obesity

• Standard fixed-dose regimens may be insufficient for patients with BMI ≥40 kg/m² or weight >120 kg 1
• Consider weight-based dosing or higher fixed-dose regimens in morbidly obese patients, though specific dalteparin data in this population is limited 1

Critical Safety Considerations

Spinal Hematoma Risk

• The most critical pitfall is performing neuraxial procedures too soon after dalteparin administration or dosing too soon after catheter removal, which dramatically increases spinal hematoma risk 1
• Always verify the exact timing of the last dalteparin dose before any neuraxial procedure 1
• Document catheter removal time precisely to ensure appropriate timing of subsequent doses 1

Bleeding Monitoring

• Major bleeding rates with prophylactic dalteparin are low (7.2% in critically ill patients with severe renal insufficiency) and comparable to unfractionated heparin 4
• All major bleeding events in renal insufficiency patients occurred with trough anti-Xa levels ≤0.18 IU/mL, well below bioaccumulation threshold 4

Pharmacokinetic Advantages

• Dalteparin has superior bioavailability and longer plasma half-life compared to unfractionated heparin, allowing once-daily dosing 6, 7
• Mean molecular weight of 5,000 daltons provides greater anti-Xa activity relative to anti-IIa activity 6
• No routine laboratory monitoring required for prophylactic doses 6, 7

Extended Prophylaxis

• Hip arthroplasty patients: Extended prophylaxis for 35 days is superior to 7 days of treatment 6
• Cancer patients: Consider extended prophylaxis duration given persistently elevated VTE risk 5