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Low Molecular Weight Heparin (LMWH) Pregnancy: Compatible — LMWH is standard VTE prevention in pregnancy (does not cross placenta)

Enoxaparin (Orthopaedic VTE Prophylaxis)

Brand names: Clexane

Adult dose

Dose: High VTE risk (THR, TKR): 40 mg SC OD starting 12h before surgery, continued for 35 days (THR) or 14 days (TKR). Moderate risk: 20–40 mg SC OD.
Route: Subcutaneous
Frequency: Once daily
Max: 40 mg OD prophylaxis; higher for treatment (1 mg/kg BD or 1.5 mg/kg OD)
If eGFR <30: use unfractionated heparin instead (LMWH accumulates in renal failure). Anti-Xa level monitoring if eGFR <30 or obesity (>100 kg). Pre-spinal/epidural: stop LMWH 12h before; restart 12h after needle removal.

Paediatric dose

Dose: 0.5 mg/kg
Route: Subcutaneous
Frequency: BD
Max: Weight-based — monitor anti-Xa levels (target 0.5–1 IU/mL)
Concentration: 20 mg/0.2 mL, 40 mg/0.4 mL, 60 mg/0.6 mL prefilled syringes mg/ml
Paediatric VTE treatment: 0.5 mg/kg BD SC. Anti-Xa monitoring essential in children (3–4h post-dose). Specialist advice required.

Dose adjustments

Renal

Reduce dose in renal impairment: eGFR 15–30: use 20 mg SC OD (prophylaxis) or UFH. Avoid if eGFR <15 (use UFH).

Hepatic

Caution in severe hepatic impairment

Paediatric weight-based calculator

Paediatric VTE treatment: 0.5 mg/kg BD SC. Anti-Xa monitoring essential in children (3–4h post-dose). Specialist advice required.

Clinical pearls

  • Spinal/epidural anaesthesia: stop 12h before needle insertion; restart 4h after needle removal (12h if traumatic insertion)
  • HIT: thrombocytopenia occurring 5–14 days after heparin start — requires immediate switch to alternative anticoagulant (argatroban/danaparoid)
  • Anti-Xa level: standard peak 3–4h post-dose; target 0.2–0.5 IU/mL prophylaxis; 0.5–1 IU/mL treatment
  • Obesity (>100 kg): consider body weight-adjusted dosing or anti-Xa monitoring

Contraindications

  • Active bleeding or high bleeding risk
  • Heparin-induced thrombocytopenia (HIT — within 100 days)
  • Severe thrombocytopenia (<50×10⁹/L)
  • Epidural/spinal anaesthesia within 12h

Side effects

  • Bleeding
  • HIT (lower risk than UFH — 0.1–0.5%)
  • Injection site bruising/haematoma
  • Hyperkalaemia (aldosterone suppression)
  • Osteoporosis (prolonged use)

Interactions

  • Anticoagulants — additive bleeding
  • NSAIDs — increased bleeding risk
  • ACEi/ARBs — hyperkalaemia risk

Monitoring

  • Platelet count (baseline; after 5–7 days — HIT monitoring)
  • Anti-Xa levels (obese, renal impairment, extremes of weight)
  • Renal function
  • Signs of bleeding

Reference: BNFc; BNF; NICE NG89 VTE Prevention; Thrombosis UK Orthopaedic Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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