What is the recommended dose and frequency for Deep Vein Thrombosis (DVT) prophylaxis?

DVT Prophylaxis Dosing and Frequency Recommendations

For DVT prophylaxis, the recommended standard dosing is enoxaparin 40 mg subcutaneously once daily or unfractionated heparin (UFH) 5000 IU subcutaneously every 8 hours, with selection based on patient factors and clinical context. 1, 2

Standard Prophylactic Dosing Options

Low Molecular Weight Heparin (LMWH)

• Enoxaparin 40 mg subcutaneously once daily 1, 2
• Dalteparin 5000 IU subcutaneously once daily 2
• Tinzaparin 4500 IU or 75 IU/kg subcutaneously once daily 2

Unfractionated Heparin (UFH)

• 5000 IU subcutaneously every 8 hours (preferred in cancer patients) 2
• Note that UFH administered 3 times daily was shown to be more effective than twice-daily dosing in preventing DVT in general surgery patients 2

Factor Xa Inhibitor

• Fondaparinux 2.5 mg subcutaneously once daily 2, 3

Duration of Prophylaxis

• Medical patients: Continue until fully ambulatory or hospital discharge 1
• Surgical patients: At least 7-10 days 1
• Hip fracture surgery: Extended prophylaxis up to 24 additional days (total of 32 days) 3
• Cancer patients: Consider extended prophylaxis, especially with ongoing risk factors 2

Special Population Considerations

Renal Impairment

• For patients with creatinine clearance <30 mL/min:
  • Reduce enoxaparin to 30 mg subcutaneously once daily 1
  • Consider UFH as the agent of choice as it's primarily metabolized by the liver 2

Obesity

• For patients with BMI >30 kg/m²:
  • Consider intermediate doses of enoxaparin (40 mg subcutaneously every 12 hours) 1
  • Alternative: weight-based dosing (0.5 mg/kg subcutaneously every 12 hours) 1

Cancer Patients

• UFH 5000 IU subcutaneously every 8 hours is the recommended regimen for VTE prophylaxis 2
• For long-term prophylaxis in cancer patients, LMWH is preferred over warfarin 2
• Dalteparin 200 IU/kg subcutaneously daily for 1 month, then 150 IU/kg subcutaneously daily for extended prophylaxis 2

Clinical Considerations and Pitfalls

• Timing of first dose is critical:

  • For surgical patients, start enoxaparin 2-4 hours preoperatively or 10-12 hours preoperatively 1
  • For fondaparinux, administer the initial dose no earlier than 6-8 hours after surgery 3
  • Administering too close to neuraxial anesthesia increases risk of spinal hematoma 1, 3

• Monitoring:

  • Routine monitoring of anti-Xa levels is not required for most patients on prophylactic doses 4
  • Consider monitoring in patients with extreme body weights or renal impairment 1

• Comparative efficacy:

  • A study comparing enoxaparin 30 mg twice daily versus 40 mg once daily found that the once-daily regimen resulted in lower DVT rates (2.9% vs 25%) and higher anti-Xa levels 5
  • Enoxaparin 20 mg once daily has been shown to be ineffective compared to 40 mg once daily in medical patients 6

• When transitioning to warfarin for long-term anticoagulation, overlap parenteral anticoagulant with warfarin for at least 5 days and until INR ≥2.0 for at least 24 hours 2

Remember that these recommendations are based on general guidelines, and clinical judgment should be exercised when applying them to individual patients with multiple comorbidities or contraindications to anticoagulation.