What is the recommended route of administration for heparin (unfractionated heparin)?

Recommended Routes of Administration for Unfractionated Heparin

The two preferred routes of administration for unfractionated heparin (UFH) are continuous intravenous (IV) infusion and subcutaneous (SC) injection. 1

Intravenous Administration

• Continuous IV infusion is the most common method for delivering therapeutic doses of heparin
• Provides immediate anticoagulant effect
• Allows for more predictable anticoagulant response
• Recommended initial dosing:
  • Bolus of 80 units/kg followed by 18 units/kg per hour for venous thromboembolism 2
  • Slightly lower dose (70 units/kg bolus followed by 15 units/kg per hour) for cardiac or stroke patients 2

Subcutaneous Administration

• Viable alternative when IV access is limited or for long-term therapy
• Important considerations for SC administration:
  • Delayed onset of action (1-2 hours) 1
  • Lower bioavailability compared to IV administration
  • Higher doses required to achieve therapeutic effect 1
  • If immediate anticoagulation is needed, an IV bolus should accompany the first SC dose 1

Bioavailability Considerations

• Low-dose SC heparin (5,000 units every 12 hours) has reduced plasma recovery 1
• Moderate-dose SC heparin (12,500-15,000 units every 12 hours) also has reduced bioavailability 1
• High-dose SC heparin (>35,000 units/24 hours) has almost complete plasma recovery 1

Route Selection Based on Clinical Scenario

For Therapeutic Anticoagulation

• Continuous IV infusion is preferred for:

  • Acute venous thromboembolism requiring immediate effect
  • Unstable patients requiring rapid dose adjustments
  • Patients with fluctuating renal function

• Subcutaneous injection is appropriate for:

  • Stable patients requiring long-term therapy
  • When IV access is problematic
  • Outpatient management scenarios

For Prophylactic Anticoagulation

• Subcutaneous injection is the standard approach:
  • General medical patients: 5,000 IU every 12 hours 2
  • Higher-risk patients (e.g., cancer): 5,000 IU every 8 hours 2

Administration Warnings

• Avoid intramuscular route due to high risk of hematoma formation 3
• For SC injections, administer deep into subcutaneous tissue (intrafat, above iliac crest or abdominal fat layer) 3
• Use different sites for each SC injection to prevent hematoma development 3

Monitoring Recommendations

• For IV therapy: Check aPTT approximately every 4 hours initially, then at appropriate intervals 3
• For SC therapy: Draw blood samples 4-6 hours after injection to assess adequacy of dosing 3
• Target aPTT of 1.5-2.3 times control value for therapeutic effect 2, 3
• Monitor platelet counts regularly to detect heparin-induced thrombocytopenia 2

The choice between IV and SC administration should be based on the clinical situation, required speed of anticoagulation, and patient-specific factors, with continuous IV infusion being the most reliable method for achieving consistent therapeutic anticoagulation.