What is the recommended dose of enoxaparin (low molecular weight heparin) for thrombophylaxis?

Enoxaparin Dosing for Thromboprophylaxis

Standard Prophylactic Dosing

The recommended dose of enoxaparin for thromboprophylaxis is 40 mg subcutaneously once daily for most patients, including hospitalized medical and surgical patients. 1, 2

• This standard dose should be continued throughout hospitalization or until the patient is fully ambulatory 2
• For surgical patients, prophylaxis should extend for at least 7-10 days postoperatively 2
• Enoxaparin offers superior pharmacologic properties compared to unfractionated heparin, including better bioavailability, longer half-life, more predictable anticoagulation, and lower risks of bleeding, heparin-induced thrombocytopenia, and osteopenia 1, 2

Dosing Adjustments for Obesity

For patients with class III obesity (BMI ≥40 kg/m²), intermediate dosing of 40 mg subcutaneously every 12 hours or weight-based dosing of 0.5 mg/kg subcutaneously every 12 hours is recommended. 1, 2

• Standard 40 mg once-daily dosing is inadequate in morbidly obese patients due to altered pharmacokinetics and increased volume of distribution 2
• Weight-based dosing of 0.5 mg/kg every 12 hours results in anti-Xa levels more consistently within the prophylactic target range compared to fixed dosing in this population 1
• For patients with class I-II obesity, consider increasing from standard prophylactic doses to higher fixed-dose regimens 2
• Anti-Xa monitoring may be considered in class III obesity to confirm adequate anticoagulation, though this is optional 2

Dosing in Renal Impairment

For patients with severe renal insufficiency (creatinine clearance <30 mL/min), reduce the prophylactic dose to 30 mg subcutaneously once daily. 2, 3

• Enoxaparin clearance is reduced by 31% in moderate renal impairment and 44% in severe renal impairment 2, 4
• In patients with severe renal disease, unfractionated heparin may be preferred over enoxaparin as it undergoes hepatic rather than renal elimination 1, 2
• For patients with severe renal impairment on prolonged therapy, monitor anti-Xa levels with a target of 0.2-0.5 IU/mL for prophylactic dosing, measured 4-6 hours after administration 2

Timing with Neuraxial Anesthesia

For prophylactic doses (40 mg daily), enoxaparin may be started 4 hours after catheter removal but not earlier than 12 hours after the neuraxial block was performed. 2, 5

• For intermediate doses (40 mg every 12 hours), wait 4 hours after catheter removal but not earlier than 24 hours after the block 2, 5
• Failure to properly time administration increases the risk of spinal hematoma 3

Special Populations

Pregnancy and Postpartum

• The standard prophylactic dose is 40 mg subcutaneously once daily 1
• For pregnant women with class III obesity requiring thromboprophylaxis, use intermediate doses of 0.5 mg/kg subcutaneously every 12 hours 1, 3
• Avoid new oral anticoagulants (apixaban, rivaroxaban, dabigatran) in pregnant or postpartum patients due to insufficient safety data 1, 2

Cancer Patients

• Standard dose is 40 mg subcutaneously once daily 2
• For cancer patients with multiple VTE risk factors, consider extended prophylaxis for up to 4 weeks after discharge 2
• Ensure appropriate weight-based or higher fixed dosing in obese cancer patients given their particularly high VTE risk 2

Common Pitfalls and Caveats

• Underdosing in obesity: Standard 40 mg once-daily dosing leads to subtherapeutic levels in patients with BMI ≥40 kg/m² 2
• Overdosing in renal failure: Failure to adjust dose in severe renal impairment (CrCl <30 mL/min) leads to drug accumulation and increased bleeding risk 2, 3
• Premature discontinuation: Most VTE events (approximately 70%) occur within the first month after surgery, with the majority occurring after hospital discharge, supporting extended prophylaxis in high-risk patients 2
• Timing errors with neuraxial procedures: Administering enoxaparin too soon after spinal/epidural anesthesia significantly increases spinal hematoma risk 2, 3
• Bleeding risk assessment: Always perform bleeding risk assessment before initiating prophylaxis, and consider delaying pharmacologic prophylaxis or using mechanical methods in patients with significant intraoperative bleeding complications 2