ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Anticoagulant — Indirect Thrombin Inhibitor Pregnancy: C

Unfractionated Heparin (IV)

Brand names: Heparin Sodium

Adult dose

Dose: 5000 units IV bolus then 18 units/kg/h infusion; adjust to APTT ratio 1.5–2.5
Route: intravenous
Frequency: continuous infusion (bolus then infusion)
Max: Protocol dependent (APTT-guided)
Use weight-based dosing nomogram; APTT-guided dose adjustment; check APTT 6h after initiation and after dose change

Paediatric dose

Route: IV
Frequency: continuous infusion
Max: 20 units/kg/h
Concentration: 1000 units/mL or 5000 units/mL (dilute for neonates) units/hour/ml
Anti-Xa monitoring preferred in neonates; target APTT ratio 1.5–2.5; check APTT 4h post-initiation

Dose adjustments

Renal

No dose adjustment required (hepatic metabolism, renal excretion minor)

Hepatic

Use with caution in severe hepatic impairment

Clinical pearls

  • Only anticoagulant in UK practice that is fully reversed by protamine sulphate (1 mg per 100 units)
  • HIT Type 2: immune-mediated; platelet drop >50% after day 5 of heparin; 4T score for probability; switch to argatroban
  • Advantage over LMWH: immediate reversal, short half-life (90 min IV), APTT monitoring

Contraindications

  • Active haemorrhage
  • History of HIT
  • Thrombocytopenia (<100 × 10⁹/L)
  • Recent neurosurgery or ophthalmological surgery

Side effects

  • Bleeding
  • HIT (Type 1 — benign, Type 2 — thrombotic: serious)
  • Osteoporosis (long-term)
  • Hyperkalaemia
  • Elevated LFTs
  • Hypersensitivity

Interactions

  • Anticoagulants/antiplatelets (bleeding)
  • GTN IV (reduces heparin effect)
  • Penicillins (may partially antagonise)

Monitoring

  • APTT ratio (target 1.5–2.5; 6h after initiation, then daily when stable)
  • Platelet count every 2–3 days (HIT monitoring)
  • Serum potassium

Reference: BNFc; BNF 86; BCSH HIT guidelines; NICE NG158. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Pathways