Antithrombin iii

Name: Antithrombin iii

Dosing & Uses

Dosage Forms & Strengths

powder for injection

  • 500 Units
  • 1000 Units

Therapeutic Goal

Prophylaxis of thrombosis during surgical or obstetrical procedures

Increase & maintain antithrombin activity between 80-120% (0.8-1.2 International Unit/mL) during treatment

Loading dose should target 100% AT activity level based on weight & pretreatment AT activity level

Determine Dosage on an Individual Basis

Base on pre-therapy plasma antithrombin III (AT-III) level

In order to increase plasma AT-III levels to that found in normal human plasma

Surgical Patients

Initial dose should raise AT levels to 120%

Load = [(120 - baseline AT activity level in %) x kg Body Weight]/1.4 = units of antithrombin required IV


  • Target subsequent dosing to keep levels between 80-120%, which may be achieved by administering 60% of initial loading dose q24hr
  • May adjust therapy by changing the dose or interval
  • Maintain target level for 2-8 days depending on type of procedure/situation

Heparin Resistance (Orphan)

Treatment of antithrombin III dependent heparin resistance requiring anticoagulation

Orphan indication sponsor

  • AT III LLC; c/o Genzyme Corporation,15 Pleasant St. Connector, P.O. Box 9322; Framingham, MA 01701

Safety & efficacy not established


Mechanism of Action

Serine protease inhibitor; important natural inhibitor of blood coagulation; inactivation of thrombin, plasmin, and other active serine proteases of coagulation including factors IXa, Xa, XIa, and XIIa.


Half-life: 2.5-3.8 days; surgery, acute thrombosis, and/or concomitant heparin may shorten half-life