Low Molecular Weight Heparin — VTE Prophylaxis Pregnancy: Safe in pregnancy — does not cross placenta; preferred anticoagulant in pregnancy

Dalteparin (Perioperative VTE Prophylaxis)

Brand names: Fragmin

Adult dose

Dose: 2500-5000 units SC once daily (prophylaxis); 200 units/kg SC once daily (treatment)

Route: Subcutaneous injection

Frequency: Once daily

Max: 5000 units/day (prophylaxis); 18000 units/day (treatment)

High VTE risk surgery: 5000 units SC starting 12 hours pre-op and continuing post-op. Moderate risk: 2500 units SC 1-2 hours pre-op. Duration: until ambulatory (minimum 7-10 days); extended 28 days for major abdominal/pelvic cancer surgery

Paediatric dose

Dose: 100 units/kg SC once daily (treatment); prophylaxis: seek specialist opinion units/kg

Route: SC

Frequency: Once or twice daily

Max: Seek specialist opinion

Seek specialist paediatric input for exact prophylaxis dosing

Dose adjustments

Renal

Accumulation risk in eGFR under 30 — measure anti-Xa levels; consider unfractionated heparin instead

Hepatic

Use with caution — increased bleeding risk

Paediatric weight-based calculator

Patient weight (kg)

Seek specialist paediatric input for exact prophylaxis dosing

Clinical pearls

Neuraxial anaesthesia timing (ESRA 2021): stop dalteparin 12 hours before neuraxial block (prophylactic dose); 24 hours (therapeutic dose); restart no earlier than 4 hours after catheter removal
NICE VTE guideline (NG89): LMWH is first-line pharmacological VTE prophylaxis for most surgical patients — rivaroxaban only for hip/knee arthroplasty
Anti-Xa monitoring: routine monitoring not recommended for prophylactic doses in standard patients; measure anti-Xa levels in obesity (BMI above 40), pregnancy, and renal impairment
Antidote: protamine partially reverses LMWH (approximately 60-70% reversal of anti-Xa activity); 1 mg protamine per 100 anti-Xa units dalteparin given in preceding 8 hours
Extended prophylaxis after major cancer surgery (28 days) reduces VTE by approximately 60% vs 7-day course — cost-effective and evidence-based

Contraindications

Active major bleeding
HIT
Severe thrombocytopenia
Epidural or spinal anaesthesia within timing window

Side effects

Bleeding
HIT (days 5-14 — lower risk than UFH)
Injection site bruising and haematoma
Hyperkalaemia
Osteoporosis (prolonged use)

Interactions

Antiplatelet agents (increased bleeding)
Warfarin / DOACs (additive anticoagulation)
NSAIDs (increased bleeding risk)

Monitoring

Signs of bleeding
Platelet count (day 5-14 — HIT surveillance)
Anti-Xa levels (high-risk patients)
Renal function

Reference: BNFc; BNF 90; NICE NG89 (VTE Prevention in Hospital); ESRA Guidelines 2021; Fragmin SPC. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Enoxaparin (Burns — VTE Prophylaxis) · Low Molecular Weight Heparin — VTE Prophylaxis

Pathways