What is the recommended dose of enoxaparin (low molecular weight heparin) for patients with acute coronary syndrome, considering impaired renal function?

Enoxaparin Dosing in Acute Coronary Syndrome

Standard Dosing for Non-ST-Elevation ACS

For patients with non-ST-elevation acute coronary syndrome, administer enoxaparin 1 mg/kg subcutaneously every 12 hours, with dose reduction to 1 mg/kg once daily in patients with creatinine clearance <30 mL/min. 1, 2

• An initial 30 mg intravenous loading dose has been used in selected patients, though this is not mandatory for all patients 1, 2
• Continue enoxaparin for the duration of hospitalization or until PCI is performed 2

Dosing for ST-Elevation MI with Fibrinolytic Therapy

The dosing strategy differs significantly based on age and renal function:

Patients <75 Years Old

• Administer 30 mg IV bolus, followed in 15 minutes by 1 mg/kg subcutaneously every 12 hours (maximum 100 mg for first 2 doses) 1, 2

Patients ≥75 Years Old

• Do not give IV bolus 1, 2
• Administer 0.75 mg/kg subcutaneously every 12 hours (maximum 75 mg for first 2 doses) 1, 2

Severe Renal Impairment (CrCl <30 mL/min)

• Regardless of age, reduce to 1 mg/kg subcutaneously every 24 hours 1, 2
• This adjustment is critical as enoxaparin clearance decreases by 44% in severe renal impairment, leading to significant drug accumulation 3

Dosing When Transitioning to PCI

The timing of the last enoxaparin dose determines additional dosing needs:

• If last subcutaneous dose was 8-12 hours earlier or only 1 dose given: Administer 0.3 mg/kg IV 2
• If last dose was within 8 hours: No additional enoxaparin needed 2
• If no prior anticoagulant therapy: Give 0.5-0.75 mg/kg IV bolus 2

Critical Renal Function Considerations

Patients with moderate renal impairment (CrCl 30-50 mL/min) warrant careful consideration for dose reduction, though current guidelines only mandate adjustment for CrCl <30 mL/min. 1, 2

• Research demonstrates that enoxaparin clearance decreases by 31% in moderate renal impairment 3
• A dosing regimen of 0.8 mg/kg every 12 hours for moderate impairment may avoid accumulation while maintaining therapeutic anti-Xa levels 3
• Patients with severe renal impairment may alternatively be managed with unfractionated heparin 1

Common Pitfalls to Avoid

• Never switch between enoxaparin and unfractionated heparin during treatment - this significantly increases bleeding risk 1, 4
• Document body weight accurately, as 9% of patients in one study lacked weight documentation to guide dosing 5
• Recognize that 23% of patients receive doses >10% or <10% of recommended dosing in real-world practice 5
• Be aware that patients ≥75 years and those receiving concomitant antiplatelet agents (especially clopidogrel) have substantially increased bleeding risk 5
• Premature discontinuation increases thrombin activity and reinfarction risk, with greatest risk in the first 4-8 hours after stopping 2
• Patients proceeding to urgent cardiac surgery while on enoxaparin have 2.6-fold increased risk of re-exploration for bleeding compared to unfractionated heparin 6

Bleeding Risk Factors

Independent predictors of bleeding include:

• Increasing age (OR 1.57 per decade for any bleeding; OR 2.56 for major bleeding) 5
• Concomitant clopidogrel (OR 7.70 for major bleeding) 5
• Concomitant NSAIDs or antiplatelet drugs (OR 2.38) 5
• Number of enoxaparin doses administered (OR 2.15 per additional dose) 5