Clinical Pathology: Hematology & Coagulation, Transfusion Medicine

• Unfractionated heparin (UFH) accelerates the anticoagulant activity of antithrombin, which inactivates factors Xa, IIa (thrombin), IXa, and XIa.

• UFH has a half-life of 1 hour, so it takes 5 to 6 hours to be cleared.

• UFH can be reversed by administering protamine, which is an arginine-rich (positively charged) protein that binds to the negatively charged heparin.

• Dosing of protamine for heparin reversal: administer 100 mg of protamine for each 100 IU/mL of heparin activity.

• The main side effect of protamine is allergic reactions that can be severe (anaphylaxis). It can also cause hypotension, bradycardia, and hypertension/pulmonary hypertension.

• Protamine is also used to reverse the anticoagulant effect of low-molecular-weight heparin, but it only partially reverses the effect of low-molecular-weight heparin.

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