AlternativeHeparin sodium
Unfractionated Heparin
Indirect thrombin inhibitor
Reserved for renal failure, peri-delivery, or massive PE — reversible with protamine.
IVSC
First-line for
- Acute massive PE
- Peri-operative bridging
- Severe renal impairment (CrCl <30)
Mechanism
Binds antithrombin → inactivates thrombin (IIa) and factor Xa equally. Large molecule — does not cross placenta.
Why pick UFH over LMWH
- R — Renal failure
- E — Emergency reversal needed (protamine)
- D — Delivery imminent (short t½)
Dosing
- IV loading
- 80 U/kg bolus then 18 U/kg/h
- Monitor
- APTT 1.5–2.5× control q6h
- Reversal
- Protamine 1 mg per 100 U
Contraindications
- AbsoluteActive major bleeding
- AbsoluteHIT (current or past)
Side effects
- Bleeding
- HIT (heparin-induced thrombocytopenia) — check platelets day 4–14
- Osteoporosis with long-term use
Fetal & maternal notes
- • Does not cross placenta (large MW). Safe fetus.
- • Safe in breastfeeding.
Key interactions
NSAIDs
Caution↑ bleeding
Warfarin
CautionSynergistic — bridging only
Clinical pearls
- 💡 Switch from LMWH to UFH at 36/40 if planning regional anaesthesia.
- 💡 Stop ≥4 h before neuraxial block.
Content last reviewed: REPLACE_ME (e.g. 2026-07)
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