Heparin, unfractionated

25.000 U/ml multidose vials (IV, subcutaneous)

Executive Summary

(July 14, 2023)

Unfractionated heparin (UFH) is an endogenous anticoagulant that enhances antithrombin,  ultimately preventing the conversion of fibrinogen to fibrin. It can be reversed by protamine (19, 30).

Adult dose for pulmonary embolism (2, 31, 29)

Adult dose for ST-elevation myocardial infarction (3, 13, 21, 29)

*Percutaneous coronary intervention

Adult dose


The dosing strategies recommended by current guidelines for myocardial infarction and pulmonary embolism are based on studies from the 1990s. There are slight differences in dosing and adjustment protocols between different indications.

Adult dose for pulmonary embolism (2, 31, 29)

Adult dose for ST-segment elevation myocardial infarction (3, 21, 29)

* Percutaneous coronary intervention

** A different dose range is recommended depending on whether a GP IIb/IIIa inhibitor is planned or not. 70 U/kg is a dose accepted in both scenarios. This simplification has been implemented to attenuate cognitive overload.

Adult dose for thromboprophylaxis (12)

LMWHs are preferred for this indication. If UFH is selected: 

Weight-based adjustment of UFH dosage

Activated partial thromboplastin time monitoring

Weight-based nomogram for heparin dosing

Initial dose 80 U/kg bolus, then 18 U/kg/h

aPTT <35 sec (<1.2 x control) 80 U/kg bolus, increase infusion rate by 4 U/kg/h

aPPT 35-45 sec (1.2-1.5 x control) 40 U/kg bolus, increase infusion rate by 2 U/kg/h

aPPT 46-70 sec (1.5-2.3 x control) No change

aPTT 71-90 sec (2.3-3.0 x control) Reduce infusion rate by 2 U/kg/h

aPTT >90 sec (<3.0 x control) Stop infusion for 1 h, then reduce infusion rate by 3 U/kg/h

Other tests to monitor UFH effect


Pulmonary embolism and UFH

Myocardial infarction and UFH

VTE prophylaxis and UFH

Mechanism of action and pharmacology


Adverse effects

Anticoagulation reversal of UFH: protamine

UFH anticoagulation reversal

Protamine overview

Pregnancy and lactation

Heparins (UFH and LMWH) are the agents of choice for treatment and prevention of VTE in pregnant women (DVT or PE), because they do not cross the placenta and therefore do not cause anticoagulation in the fetus (24, 23). 

Pregnancy risk classification



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