What is the recommended dose of low molecular weight heparin (LMWH), specifically enoxaparin (generic name), for prophylaxis against deep vein thrombosis (DVT) and pulmonary embolism (PE) in adult patients with recent surgery, trauma, cancer, or a history of DVT or PE, including those with impaired renal function?

Low Molecular Weight Heparin (Enoxaparin) Dosing

For DVT/PE prophylaxis, use enoxaparin 40 mg subcutaneously once daily in most medical and surgical patients, starting 2-4 hours preoperatively or within 24 hours of admission, and continuing throughout hospitalization or until full ambulation. 1

Prophylactic Dosing by Clinical Context

Standard Surgical and Medical Patients

• 40 mg subcutaneously once daily is the standard prophylactic dose for most patients undergoing major surgery or hospitalized with acute medical illness 1, 2
• Start 2-4 hours before surgery or within 24 hours of hospital admission 2
• Continue for at least 7-10 days postoperatively, or throughout hospitalization for medical patients 1, 2

Extended Prophylaxis for Cancer Surgery

• Continue prophylaxis for up to 30 days after major abdominal or pelvic cancer surgery, as this reduces VTE risk by 60% without increasing bleeding 3
• High-dose prophylaxis (enoxaparin 40 mg once daily or dalteparin 5000 U once daily) is more effective than lower doses in cancer patients 3

Alternative Regimen for Orthopedic Surgery

• 30 mg subcutaneously every 12 hours demonstrates superior efficacy in knee arthroplasty when started 12-24 hours post-surgery 1

Therapeutic Dosing for Established DVT/PE

Standard Treatment Regimen

• 1 mg/kg subcutaneously every 12 hours is the preferred therapeutic regimen, providing consistent anticoagulation equivalent to unfractionated heparin 1, 3
• Alternative: 1.5 mg/kg subcutaneously once daily 1, 2
• Continue for minimum 5-10 days, overlapping with warfarin until INR ≥2.0 for at least 24 hours 1, 4

Duration of Anticoagulation

• Provoked DVT/PE (surgery, trauma): Treat for exactly 3 months 2, 4
• Unprovoked DVT/PE: Minimum 3-6 months initially, then evaluate for indefinite therapy 2, 4
• Cancer-associated VTE: Continue enoxaparin for at least 6 months, and indefinitely while cancer remains active 3, 2
• After the first month of cancer treatment, consider dose reduction to 75-80% of initial dose (e.g., dalteparin reduced from 200 to 150 units/kg daily in the CLOT study) 3

Critical Dose Adjustments for Special Populations

Severe Renal Insufficiency (CrCl <30 mL/min)

• Prophylaxis: 30 mg subcutaneously once daily 1, 2, 3
• Treatment: 1 mg/kg subcutaneously every 24 hours (instead of every 12 hours) 1, 3
• Enoxaparin clearance is reduced by 44% in severe renal impairment, significantly increasing bleeding risk 3, 2
• Monitor anti-Xa levels (target 0.5-1.5 IU/mL) in patients with severe renal impairment on prolonged therapy 1, 2

Important caveat: Some evidence suggests dose adjustments may be needed even with CrCl 30-60 mL/min, though specific recommendations vary 3. In contrast, dalteparin and tinzaparin show less bioaccumulation in renal impairment and may be safer alternatives in this population 3.

Obesity (BMI >30 kg/m²)

• Consider 40 mg subcutaneously every 12 hours for prophylaxis, or weight-based dosing at 0.5 mg/kg subcutaneously every 12 hours 1, 2
• For therapeutic dosing with BMI ≥40 kg/m², use 0.8 mg/kg subcutaneously every 12 hours instead of standard 1 mg/kg 2
• Standard fixed dosing may be inadequate in obese patients 2

Pregnancy with Class III Obesity

• Use intermediate doses of 0.5 mg/kg subcutaneously every 12 hours for thromboprophylaxis 2, 5
• Monitor anti-Xa levels in pregnant patients on therapeutic doses 2, 5

Critical Timing with Neuraxial Anesthesia

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

Specific Timing Guidelines

• Prophylactic doses (40 mg once daily): May start as early as 4 hours after catheter removal, but not earlier than 12 hours after the block was performed 1, 2, 5
• Intermediate (40 mg every 12 hours) or therapeutic doses: May start as early as 4 hours after catheter removal, but not earlier than 24 hours after the block 2, 5

Monitoring Recommendations

Routine Monitoring

• Platelet counts every 2-3 days from day 4 to day 14 to screen for heparin-induced thrombocytopenia 1, 2
• Baseline CBC, renal and hepatic function, aPTT, and PT/INR before starting therapy 2
• Follow-up hemoglobin, hematocrit, and platelets every 2 weeks or as clinically indicated 2

Anti-Xa Level Monitoring (When Indicated)

• Target peak anti-Xa: 0.6-1.0 IU/mL for twice-daily dosing or 1.0-1.5 IU/mL for once-daily dosing 2
• Measure 4-6 hours after dosing, after patient has received 3-4 doses 2
• Indicated for: severe renal impairment on prolonged therapy, pregnant patients on therapeutic doses, and morbid obesity 1, 2, 5

Advantages Over Unfractionated Heparin

Enoxaparin offers several key advantages: 2, 5

• Better bioavailability and longer half-life
• More predictable anticoagulation effect without need for monitoring in most patients
• Once or twice-daily dosing enabling outpatient treatment
• Lower risk of heparin-induced thrombocytopenia
• Lower risk of osteopenia with long-term use

Important Clinical Caveats

Hepatic Dysfunction

• Enoxaparin is primarily eliminated renally, not hepatically, making it safer than unfractionated heparin in liver dysfunction 2
• Elevated transaminases (ALT/AST) alone without coagulopathy do not require dose adjustment 2
• Avoid in moderate-to-severe liver disease with hepatic coagulopathy 2

When to Use Unfractionated Heparin Instead

• Severe renal impairment (CrCl <30 mL/min) where shorter half-life and reversibility with protamine are advantageous 3
• Active bleeding requiring rapid reversal 3

Common Pitfalls

• Failure to adjust dose in renal impairment leads to drug accumulation and increased bleeding risk 2
• Not timing enoxaparin appropriately with neuraxial procedures increases spinal hematoma risk 2
• Using standard fixed dosing in very obese or very low-weight patients may result in under- or over-anticoagulation 2
• Switching between enoxaparin and unfractionated heparin increases bleeding risk and should be avoided 2