What are the contraindications to prophylactic enoxaparin (low molecular weight heparin)?

Contraindications to Prophylactic Enoxaparin

Prophylactic enoxaparin is contraindicated in patients with thrombocytopenia with a positive in vitro test for antiplatelet antibody in the presence of the drug, history of heparin-induced thrombocytopenia, known sensitivity to enoxaparin/heparin/sulfites/benzyl alcohol/pork products, active major bleeding at any site/tissue/organ, and in patients aged 90 years or older with creatinine clearance less than 60 ml/min. 1

Absolute Contraindications

• Active major bleeding at any site, tissue or organ 1
• Thrombocytopenia with a positive in vitro test for antiplatelet antibody in the presence of enoxaparin or history of heparin-induced thrombocytopenia (HIT) 1
• Known sensitivity to enoxaparin, heparin, sulfites, benzyl alcohol, or pork products 1
• Age ≥90 years with creatinine clearance <60 ml/min 1

Conditions Requiring Extreme Caution (Relative Contraindications)

• Severe renal impairment (creatinine clearance <30 ml/min) 1

  • Requires dose adjustment or alternative anticoagulation
  • Enoxaparin is primarily excreted by the kidneys, leading to potential accumulation and increased bleeding risk

• Liver failure with elevated INR (>1.5) 1

• Uncontrolled arterial hypertension (systolic >200 mmHg, diastolic >110 mmHg) 1

• Thrombocytopenia of any degree requires active monitoring 1

• Recent or planned neuraxial anesthesia (epidural/spinal) 1

  • Avoid LMWH 12 hours before manipulation of epidural/spinal catheter
  • Can administer 2 hours after epidural catheter removal

Special Population Considerations

Renal Impairment

• For patients with creatinine clearance <30 ml/min:
  • Consider dose reduction to 30 mg once daily 1
  • Consider alternative anticoagulants 1
  • Monitor anti-Xa levels if using enoxaparin 2

Elderly Patients

• Use with caution in elderly patients, especially those with renal impairment 1
• Patients ≥75 years with STEMI may require dose adjustment (0.75 mg/kg SC every 12 hours without initial IV bolus) 1

Obese Patients

• Standard prophylactic dosing may be inadequate in morbidly obese patients (BMI ≥40 kg/m²) 1, 2
• Consider weight-based dosing (0.5 mg/kg twice daily) 2

Underweight Patients

• Use caution in patients weighing less than 50 kg 1, 2

Monitoring Recommendations

• Complete blood count monitoring:

  • Baseline hemoglobin, hematocrit, and platelet count
  • Every 2-3 days up to at least day 14 of therapy
  • Every 2 weeks thereafter or as clinically indicated 1

• Renal function monitoring:

  • Baseline creatinine clearance
  • Regular monitoring in patients with renal impairment
  • Approximately 13% of patients may develop GFR <30 ml/min/1.73 m² during follow-up 1

• Anti-Xa monitoring may be considered in:

  • Severe renal insufficiency
  • Morbid obesity
  • Pediatric patients
  • Pregnant women 2

Clinical Pitfalls to Avoid

• Failure to recognize HIT: Monitor platelet count regularly and be vigilant for thrombocytopenia, which could indicate HIT 1

• Switching between anticoagulants: Patients initially treated with enoxaparin should not be switched to unfractionated heparin and vice versa due to increased bleeding risk 1

• Inadequate dosing in obesity: Standard fixed dosing may be inadequate in morbidly obese patients 1, 2

• Overlooking renal function: Enoxaparin accumulation in renal impairment can lead to bleeding complications 1

• Concomitant use with other anticoagulants or antiplatelets: Significantly increases bleeding risk 2

By carefully screening for these contraindications and using appropriate caution in special populations, the risk of adverse events with prophylactic enoxaparin can be minimized while maintaining its thromboprophylactic benefits.