What Low Molecular Weight Heparin (LMWH) is recommended for deep vein thrombosis or pulmonary embolism?

LMWH Selection for DVT/PE Treatment

For most patients with deep vein thrombosis or pulmonary embolism, enoxaparin 1 mg/kg subcutaneously every 12 hours is the preferred LMWH regimen, with dalteparin or tinzaparin as acceptable alternatives. 1, 2

Primary LMWH Options

The three most widely validated LMWHs for VTE treatment are:

• Enoxaparin: 1 mg/kg subcutaneously every 12 hours (most extensively studied regimen) 1, 2
• Dalteparin: 200 IU/kg once daily (maximum 18,000 IU) 1, 3
• Tinzaparin: 175 IU/kg once daily 1

All three agents have demonstrated superior efficacy compared to unfractionated heparin, with significantly reduced mortality (approximately 50% reduction), fewer major bleeding episodes, and lower rates of recurrent thromboembolism. 1, 4

Dosing Algorithm by Clinical Scenario

Standard DVT/PE Treatment

• First-line: Enoxaparin 1 mg/kg every 12 hours subcutaneously 1, 2
• Alternative once-daily option: Enoxaparin 1.5 mg/kg once daily (FDA-approved for inpatient PE treatment in the US, though twice-daily dosing has stronger validation) 1, 2

Severe Renal Impairment (CrCl <30 mL/min)

• Switch to unfractionated heparin (preferred due to hepatic clearance, shorter half-life, and reversibility with protamine) 1
• If LMWH must be used: Reduce enoxaparin to 1 mg/kg once daily (every 24 hours) with mandatory anti-Xa monitoring 2, 5
• Anti-Xa levels are significantly elevated in renal impairment (median 1.34 IU/mL vs 0.91 IU/mL in normal function), creating substantial bleeding risk 5

Cancer-Associated Thrombosis

• Preferred: Dalteparin 200 IU/kg once daily for 1 month, then 150 IU/kg once daily for 5 months, followed by indefinite anticoagulation 1, 2, 3
• Alternative: Enoxaparin 1 mg/kg every 12 hours as LMWH monotherapy (do not transition to warfarin) 1, 2
• LMWH reduces recurrent VTE by 42% compared to warfarin in cancer patients (8.0% vs 15.8%, HR 0.48) 2
• Continue LMWH indefinitely while cancer remains active rather than switching to oral anticoagulants 1, 2

History of Heparin-Induced Thrombocytopenia (HIT)

• Use fondaparinux (5 mg for <50 kg, 7.5 mg for 50-100 kg, or 10 mg for >100 kg once daily) 1
• Fondaparinux is rarely associated with HIT development 1

Critical Safety Monitoring

Platelet Monitoring

• Check platelet count every 2-3 days for first 14 days, then every 2 weeks 2
• Hold LMWH if platelets fall below 50,000/mcL due to significantly increased bleeding risk 2

Anti-Xa Monitoring (Generally NOT Required)

• Standard dosing does not require monitoring 1
• Mandatory monitoring only in severe renal impairment (CrCl <30 mL/min) receiving prolonged treatment 2, 5

Common Pitfalls to Avoid

1. Neuraxial anesthesia timing: Do not administer enoxaparin within 10-12 hours of spinal/epidural procedures 2

2. Renal dosing errors: Failure to adjust dose in CrCl <30 mL/min leads to drug accumulation and bleeding 2, 5

3. Cancer patient transitions: Switching cancer patients from LMWH to warfarin increases recurrent VTE risk by >50% 1, 2

4. Once-daily treatment dosing in obesity: Avoid once-daily enoxaparin 1.5 mg/kg for treatment in patients >120 kg without anti-Xa monitoring 2

5. Assuming LMWH equivalence: While often used interchangeably, enoxaparin, dalteparin, and tinzaparin differ in molecular weight, half-life, and factor Xa/IIa inhibition ratios 1

Advantages Over Unfractionated Heparin

LMWH provides multiple benefits that make it superior to unfractionated heparin:

• Mortality reduction: Statistically significant 3-month survival benefit 1
• Reduced bleeding: Fewer major hemorrhagic complications 1, 4
• No monitoring required: Fixed weight-based dosing eliminates need for aPTT checks 1
• Outpatient treatment: Once or twice-daily subcutaneous administration enables home therapy 1
• Lower HIT risk: Significantly reduced incidence of heparin-induced thrombocytopenia 1, 4
• Cost savings: Eliminates hospitalization and laboratory monitoring costs 1