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Anticoagulant — Low Molecular Weight Heparin Pregnancy: Preferred anticoagulant in pregnancy — does not cross placenta; anti-Xa monitoring required in pregnancy

Dalteparin (Orthopaedic VTE Prophylaxis)

Brand names: Fragmin

Adult dose

Dose: 2500 units SC 2 hours pre-op, then 2500 units 4–8 hours post-op, then 5000 units once daily; hip fracture: 5000 units once daily
Route: Subcutaneous
Frequency: Once daily (maintenance)
Max: 5000 units once daily
THR/TKR: continue 5 weeks post-op. Hip fracture: start as soon as haemostasis achieved (day 1–2 post-op); continue 5 weeks. Rotate injection sites. Anti-Xa monitoring not routinely needed at prophylactic doses.

Paediatric dose

Dose: 100 units/kg
Route: Subcutaneous
Frequency: Once daily
Max: 5000 units/day
Paediatric VTE prophylaxis under specialist guidance — off-label; anti-Xa monitoring recommended

Dose adjustments

Renal

Use with caution if eGFR <30 mL/min — accumulation risk; consider UFH alternatively; anti-Xa monitoring if used in severe renal impairment

Hepatic

Use with caution in severe hepatic impairment — coagulopathy increases bleeding risk

Paediatric weight-based calculator

Paediatric VTE prophylaxis under specialist guidance — off-label; anti-Xa monitoring recommended

Clinical pearls

  • LMWH remains the backbone of orthopaedic VTE prophylaxis in the UK — dalteparin and enoxaparin are the most commonly used
  • HIT type 2 monitoring: check platelet count at day 5–7 in all patients receiving heparin for >4 days — if HIT suspected, STOP all heparin immediately; switch to argatroban or fondaparinux
  • Neuraxial anaesthesia: remove epidural catheter ≥10–12 hours after last LMWH dose; next LMWH dose ≥4 hours after catheter removal — follow regional anaesthesia/anticoagulation joint guidelines (ASRA/ESRA)
  • Anti-Xa monitoring: not routine at prophylactic doses; use for pregnancy, extremes of weight, and renal impairment
  • Spinal cord injury VTE prophylaxis: LMWH within 72 hours if no contraindication — high VTE risk without prophylaxis (DVT in 50–100% without prophylaxis)

Contraindications

  • Active significant bleeding
  • Severe thrombocytopenia
  • HIT type 2 (type II heparin-induced thrombocytopenia)
  • Regional anaesthesia with concurrent therapeutic anticoagulation

Side effects

  • Bleeding — most important clinical risk
  • HIT type 2 — fall in platelet count >50% from baseline at days 5–14; immune-mediated; thrombotic paradox
  • Injection site bruising and haematoma
  • Osteoporosis with prolonged use (>3 months)
  • Elevated LFTs (transient)

Interactions

  • Other anticoagulants and antiplatelets — additive bleeding
  • NSAIDs — increased bleeding risk
  • ACE inhibitors — hyperkalaemia risk (all heparins inhibit aldosterone)

Monitoring

  • Platelet count at baseline and day 5–7 (HIT monitoring)
  • Renal function
  • Anti-Xa levels if indicated (extremes of weight, renal impairment)
  • Signs of bleeding

Reference: BNFc; BNF 90; NICE NG89; NICE NG158 (Venous Thromboembolism in Pregnancy); ESRA Guidelines (Neuraxial Anaesthesia and Anticoagulation); SPC Fragmin. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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