What is the dosage and usage of Enoxaparin (low molecular weight heparin) for prevention and treatment of deep vein thrombosis and pulmonary embolism?

Enoxaparin Dosing and Administration

Prophylactic Dosing for DVT Prevention

For DVT prophylaxis in medical and surgical patients, administer enoxaparin 40 mg subcutaneously once daily, starting 2-4 hours preoperatively or within 24 hours of hospital admission, and continuing throughout hospitalization or until the patient is fully ambulatory. 1, 2

Standard Prophylactic Regimens:

• 40 mg subcutaneously once daily is the standard dose for most medical and surgical patients 1, 3, 2
• Duration: entire hospital stay or until full ambulation for medical patients; minimum 7-10 days for surgical patients 1, 2
• Alternative regimen: 30 mg subcutaneously every 12 hours has demonstrated superior efficacy in knee arthroplasty when started 12-24 hours post-surgery 1, 2

Advantages Over Unfractionated Heparin:

• Better bioavailability and longer half-life 1, 3
• More predictable anticoagulation effect 1, 3
• Lower risk of heparin-induced thrombocytopenia and osteopenia 1, 3
• Lower risk of major bleeding 1

Therapeutic Dosing for DVT/PE Treatment

For treatment of established DVT or PE, administer enoxaparin 1 mg/kg subcutaneously every 12 hours, which provides consistent therapeutic anticoagulation with proven efficacy equivalent to unfractionated heparin. 1, 2, 4

Standard Therapeutic Regimens:

• Primary regimen: 1 mg/kg subcutaneously every 12 hours 1, 3, 2, 4
• Alternative regimen: 1.5 mg/kg subcutaneously once daily 1, 3, 2, 4
• Initial treatment duration: typically 5-10 days, overlapping with warfarin until INR >2.0 for 2 consecutive days 1, 2
• For cancer patients: extended treatment for at least 3-6 months, with consideration for dose reduction after the first month 1

Evidence for Equivalence:

Both once-daily and twice-daily therapeutic enoxaparin regimens have been shown to be equivalent to dose-adjusted unfractionated heparin in terms of symptomatic VTE recurrence and major hemorrhage 1, 4. The once-daily regimen offers improved patient compliance, reduced healthcare worker exposure, and potentially lower treatment costs 1.

Dose Adjustments for Special Populations

Severe Renal Impairment (CrCl <30 mL/min):

Dose reduction is mandatory due to 44% reduction in enoxaparin clearance, which significantly increases bleeding risk. 1, 3, 2

• Prophylactic dose: 30 mg subcutaneously once daily 1, 3, 2
• Therapeutic dose: 1 mg/kg subcutaneously every 24 hours 1, 3
• Renal clearance is reduced by 31% in moderate impairment and 44% in severe impairment 1, 3

Obesity (BMI >30 kg/m²):

• Consider intermediate doses: 40 mg subcutaneously every 12 hours 1, 3, 2
• Alternative: weight-based dosing at 0.5 mg/kg subcutaneously every 12 hours 1, 3, 2
• For BMI ≥40 kg/m²: use 0.8 mg/kg subcutaneously every 12 hours for therapeutic dosing 1
• For patients with weight >150 kg at high risk: consider 40 mg every 12 hours for prophylaxis 3

Pregnancy with Class III Obesity:

• Intermediate doses: 0.5 mg/kg subcutaneously every 12 hours for thromboprophylaxis 1

Hepatic Dysfunction:

Enoxaparin is primarily eliminated renally, not hepatically, making it safer than unfractionated heparin in patients with liver dysfunction. 1

• Elevated transaminases (ALT/AST) without coagulopathy do not contraindicate enoxaparin use 1
• Avoid in moderate-to-severe liver disease with hepatic coagulopathy 1
• Elevated liver enzymes alone do not require dose adjustment 1

Critical Timing Considerations with Neuraxial Anesthesia

Avoid enoxaparin administration within 10-12 hours before neuraxial anesthesia or spinal catheter removal to prevent spinal hematoma. 1, 3, 2

Timing Guidelines:

• Prophylactic doses (40 mg once daily): may be started as early as 4 hours after catheter removal but not earlier than 12 hours after the block was performed 1, 3, 2
• Intermediate (40 mg every 12 hours) or therapeutic doses: may be started as early as 4 hours after catheter removal but not earlier than 24 hours after the block 3
• Preoperative timing: start 2-4 hours preoperatively or 10-12 hours preoperatively for neuraxial anesthesia 1, 3

Monitoring Recommendations

Anti-Xa Level Monitoring:

Monitor anti-Xa levels in patients with severe renal impairment on prolonged therapy, targeting 0.5-1.5 IU/mL. 1, 2

• Measure 4-6 hours after dosing, after patient has received 3-4 doses 1
• Target peak anti-Xa level for once-daily therapeutic dosing: 1.0-1.5 IU/mL 1
• Target peak anti-Xa level for twice-daily therapeutic dosing: 0.6-1.0 IU/mL 1
• Also monitor in pregnant patients on therapeutic doses and patients with morbid obesity 3
• Routine monitoring is generally not necessary for most patients 1

Platelet Monitoring:

Monitor platelet counts every 2-3 days from day 4 to day 14 to screen for heparin-induced thrombocytopenia. 1, 2

• Follow-up monitoring: hemoglobin, hematocrit, and platelet count at least every 2-3 days for the first 14 days and every 2 weeks thereafter 1

Baseline Laboratory Testing:

• CBC, renal and hepatic function panel, aPTT, and PT/INR 1
• Always check creatinine clearance before initiating enoxaparin, as this determines dosing more than liver function 1

Common Pitfalls and Caveats

Critical Warnings:

• Failure to properly time enoxaparin administration with spinal/epidural procedures can increase the risk of spinal hematoma 1
• Not adjusting the dose in patients with renal impairment can lead to drug accumulation and increased bleeding risk 1
• Standard fixed dosing may be inadequate in obese patients and excessive in very low-weight patients 1
• Avoid switching between enoxaparin and unfractionated heparin due to increased bleeding risk 1
• Use cautiously with other antiplatelet or anticoagulant medications due to increased bleeding risk 1

Special Considerations:

• In major trauma, generally withhold enoxaparin for 2-3 days, then reassess risk-benefit ratio before initiating 3
• For patients with high bleeding risk, consider mechanical prophylaxis (graduated compression stockings and/or intermittent pneumatic compression) 3