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Low Molecular Weight Heparin (LMWH) Pregnancy: Safe throughout pregnancy. LMWH of choice for VTE in pregnancy (RCOG Green-Top Guidelines).

Enoxaparin

Brand names: Clexane

Adult dose

Dose: Treatment: 1.5 mg/kg SC once daily or 1 mg/kg SC twice daily; Prophylaxis: 40 mg SC once daily
Route: Subcutaneous
Frequency: Once daily (treatment/prophylaxis) or twice daily (treatment)
Max: 180 mg/dose (treatment)
VTE treatment: 1.5 mg/kg SC OD (or 1 mg/kg SC BD in active cancer/high risk). Prophylaxis: 20 mg SC OD (moderate risk) or 40 mg SC OD (high risk). ACS/NSTEMI: 1 mg/kg SC every 12 hours. Bridging: per protocol.

Paediatric dose

Dose: 1.5 mg/kg
Route: SC
Frequency: Once daily (or BD for high risk)
Max: 40 mg prophylaxis; 1.5 mg/kg/dose treatment
Concentration: 100 mg/ml
Neonates: 1.5 mg/kg SC BD. Infants <2 months: 1.5 mg/kg BD. 2 months–17 years: 1 mg/kg BD. Prophylaxis (>2 months): 0.5 mg/kg BD. Target anti-Xa: 0.5–1.0 IU/mL (treatment).

Dose adjustments

Renal

If eGFR <30: use 1 mg/kg once daily (reduced frequency); monitor anti-Xa levels. Avoid if eGFR <15.

Hepatic

Use with caution in severe hepatic impairment.

Paediatric weight-based calculator

Neonates: 1.5 mg/kg SC BD. Infants <2 months: 1.5 mg/kg BD. 2 months–17 years: 1 mg/kg BD. Prophylaxis (>2 months): 0.5 mg/kg BD. Target anti-Xa: 0.5–1.0 IU/mL (treatment).

Clinical pearls

  • Cannot be fully reversed with protamine (only partial)
  • Anti-Xa levels needed in obesity (>120 kg), pregnancy, and renal impairment
  • Preferred LMWH for ACS and VTE in UK practice
  • Inject into abdomen (alternating sides) — avoid area 2 inches around navel
  • Spinal anaesthesia: withhold at least 12 hours before (prophylaxis) or 24 hours (treatment)

Contraindications

  • Active major bleeding
  • Thrombocytopenia with positive anti-platelet factor 4 antibody (HIT history)
  • Recent spinal/epidural anaesthesia (timing dependent)

Side effects

  • Bleeding
  • Injection site bruising and haematoma
  • HIT (less common than UFH)
  • Osteoporosis (long-term)
  • Hyperkalaemia
  • Elevated transaminases

Interactions

  • Antiplatelet drugs and NSAIDs — increased bleeding risk
  • No reversal agent (protamine only 60% effective for LMWH)

Monitoring

  • Anti-Xa levels (select patients)
  • Platelet count (days 4–14)
  • Renal function
  • Signs of bleeding

Reference: BNFc; BNF; NICE NG158; RCOG GTG 37a; BNFc. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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