What is the prophylaxis dose of Lovenox (enoxaparin) for a patient weighing 155 kg with a BMI of 45?

Prophylactic Enoxaparin Dosing for a 155 kg Patient with BMI 45

For a patient weighing 155 kg with a BMI of 45, the recommended prophylactic dose of enoxaparin is 40 mg subcutaneously twice daily. 1

Rationale for Dosing in Severe Obesity

Patients with class 3 obesity (BMI ≥40) require special consideration for VTE prophylaxis due to increased thrombotic risk and altered pharmacokinetics of enoxaparin:

• Standard fixed dosing (40 mg once daily) is likely to result in underdosing in patients with BMI ≥40 or weight >120 kg 1
• The European Society of Cardiology Working Group recommends higher fixed-dose or weight-based dosing for obesity class ≥2 (BMI ≥35) 1

Evidence-Based Dosing Options:

1. Fixed higher dose approach: 40 mg subcutaneously twice daily (recommended for this patient) 1

2. Weight-based approach: 0.5 mg/kg subcutaneously once or twice daily 1

   • For this 155 kg patient, this would equal 77.5 mg per dose
   • However, fixed higher dosing has more established evidence in guidelines

Monitoring Considerations

• Anti-Xa monitoring is not routinely required but may be considered in select cases 1
• Target prophylactic anti-Xa level range is 0.2-0.4 units/mL when measured 4 hours after the third or fourth dose 2
• Recent evidence suggests that patients with BMI ≥40 kg/m² may require doses higher than 0.5 mg/kg/day to achieve target anti-Xa levels 2

Clinical Considerations and Pitfalls

• Common pitfall: Using standard prophylactic dosing (40 mg once daily) in severely obese patients, which significantly increases VTE risk
• Important caveat: Higher dosing may increase bleeding risk, though meta-analyses suggest higher-than-standard dosing decreases VTE (OR 0.47) without significantly increasing bleeding 1
• Special situation - bariatric surgery: For post-bariatric surgery patients, higher fixed doses (40 mg twice daily) are specifically recommended for class 3 obesity 1

Alternative Options

If enoxaparin is contraindicated or unavailable, alternative LMWH options include:

• Dalteparin 5000 units subcutaneously twice daily 1
• Tinzaparin 4500 units subcutaneously twice daily 1

Duration of Therapy

• Continue prophylaxis throughout hospitalization
• For high-risk patients (especially post-bariatric surgery), extended prophylaxis may be appropriate as most VTEs occur after discharge (approximately 70% within the first month) 1

The evidence strongly supports that patients with severe obesity require higher than standard prophylactic dosing of enoxaparin to achieve adequate VTE prevention, with 40 mg twice daily being the most appropriate regimen for this 155 kg patient with BMI 45.