What dose of enoxaparin (Lovenox) should be administered to a 95‑lb patient with normal renal function?

Enoxaparin Dosing for a 95-Pound Patient

For a 95-pound (43 kg) patient with normal renal function, administer enoxaparin 40 mg subcutaneously once daily for prophylaxis or 43 mg (1 mg/kg) subcutaneously every 12 hours for therapeutic anticoagulation.

Weight-Based Dosing Calculation

• A 95-pound patient weighs approximately 43 kg (95 lb ÷ 2.2 = 43.2 kg).
• Prophylactic dosing: The standard dose is 40 mg subcutaneously once daily, which does not require weight-based adjustment in this patient 1.
• Therapeutic dosing: Use 1 mg/kg subcutaneously every 12 hours, which equals 43 mg every 12 hours for this patient 1, 2.
• Alternatively, therapeutic dosing can be given as 1.5 mg/kg once daily, which would be 65 mg once daily 1.

Critical Considerations for Low Body Weight

• Patients weighing less than 50 kg are at higher risk for bleeding complications even with standard dosing 3, 4.
• For prophylactic dosing in patients weighing less than 45 kg with preserved renal function, consider reducing the fixed dose to 30 mg once daily 4.
• Weight-based therapeutic dosing (1 mg/kg every 12 hours) is preferred over fixed dosing in underweight patients to avoid excessive anticoagulation 1, 2.

Renal Function Assessment is Mandatory

• Always calculate creatinine clearance before initiating enoxaparin, as near-normal serum creatinine may mask severe renal dysfunction, especially in patients with low body weight 4, 2.
• If creatinine clearance is less than 30 mL/min, reduce prophylactic dosing to 30 mg once daily and therapeutic dosing to 1 mg/kg once every 24 hours (instead of every 12 hours) 1, 4, 2.
• The combination of low body weight and renal impairment represents dual high-risk factors for bleeding, requiring both dose reduction and close monitoring 4, 2.

Monitoring Recommendations

• Anti-Xa monitoring is recommended for underweight patients (less than 50 kg) receiving therapeutic enoxaparin, particularly if renal impairment coexists 3, 1.
• Draw anti-Xa levels 4–6 hours after the dose, after 3–4 consecutive doses have been administered 1, 2.
• Target prophylactic anti-Xa range: 0.2–0.5 IU/mL 1.
• Target therapeutic anti-Xa range: 0.5–1.0 IU/mL for twice-daily dosing or 1.0–1.5 IU/mL for once-daily dosing 1, 2.

Common Pitfalls to Avoid

• Do not use fixed-dose prophylaxis (40 mg daily) without considering body weight in patients weighing less than 45 kg, as this may result in relative overdosing 4.
• Never assume normal renal function based solely on serum creatinine in low-weight patients—always calculate creatinine clearance using the Cockcroft-Gault equation 4, 2.
• Avoid switching between enoxaparin and unfractionated heparin mid-treatment, as this increases bleeding risk 2.
• Do not initiate therapeutic enoxaparin without first confirming adequate renal function, as enoxaparin clearance is reduced by 44% in severe renal impairment 2.