ATryn normalizes and maintains antithrombin activity levels using approved dosing formulae1

ATryn uses Approved dosing formulae for surgical and pregnant HD AT patients, including loading dose, continuous infusion of the maintenance dose and AT activity monitoring1

Dosing Table for Surgical Patients1

Loading Dose (IU) Maintenance Dose (IU/h)
(100-baseline AT activity level)
X body weight (kg)
(100-baseline AT activity level)
X body weight (kg)

Pregnant patients require a higher dose of antithrombin (AT) due to higher clearance and volume of distribution1

Dosing Table for Pregnant Patients1

Loading Dose (IU) Maintenance Dose (IU/h)
(100-baseline AT activity level)
X body weight (kg)
(100-baseline AT activity level)
X body weight (kg)


The goal in administering ATryn is to restore and maintain functional AT activity levels between 80% and 120% of normal (0.8-1.2 IU/mL)1

Treatment Goal: AT activity levels of 80-120%
  • In clinical trials, ATryn was administered as a loading dose infusion followed by continuous infusion for at least 3 days, usually starting 1 day prior to surgery or delivery 1*
  • 85% of patient samples on the last day of dosing demonstrated normalized AT activity levels (80%-120%) with ATryn2
    • • 4% were <80% and 11% were >120%2
  • AT activity monitoring is required for proper treatment. Check AT activity once or twice per day, and make dose adjustments according to the table below1

AT Monitoring Table1

Initial Monitor Time
AT Level
Dose Adjustment
Recheck AT Level
2 Hours After Initiation of Treatment
Increase 30%
2 hours after each dose adjustment
80% to 120%
2 hours after initiation of treatment or dose adjustment
Decrease 30%
2 hours after each dose adjustment
  • Initiate treatment prior to delivery or approximately 24 hours prior to surgery to ensure that the plasma AT level is in the target range 1
  • Administer the loading dose as a 15-minute intravenous infusion, and immediately follow it with a continuous infusion of the maintenance dose1
  • AT enhances the anticoagulant effect of heparin and low molecular weight heparin (LMWH). Concurrent use of ATryn with heparin and LMWH must be monitored clinically and biologically to avoid excessive anticoagulation1
  • As surgery or delivery may rapidly decrease AT activity level, check AT level just after surgery or delivery. If the level is <80%, an additional bolus dose may be administered to restore it. Calculate this dose using the last available AT activity reading. Thereafter, restart the maintenance dose at the rate of infusion used before the bolus1
  • Continue treatment until adequate follow-on anticoagulation is established1
  • Each carton contains one single-dose vial of ATryn. The actual potency of ATryn is stated on the vial label and carton (approximately 525 IU or 1750 IU/vial)1
  • Store ATryn refrigerated between 2°C and 8°C (36°F and 46°F); after reconstitution, discard unused portion1

*Data were from 2 prospective, single-arm, open-label studies assessing 20 pregnant patients and 11 surgical patients with HD AT (N=31). Patients had AT activity levels ≤60% of normal and a history of thromboembolic events.2

27 samples obtained from 23 patients with HD AT in the peri-operative period.2

References: 1. ATryn [package insert] Framingham, MA: rEVO Biologics, December 2013.

Indications and Usage

ATryn is a recombinant antithrombin indicated for the prevention of peri-operative and peri-partum thromboembolic events in hereditary antithrombin deficient patients.

It is not indicated for treatment of thromboembolic events in hereditary antithrombin deficient patients.


Important Safety Information

ATryn is contraindicated in patients with known hypersensitivity to goat and goat milk proteins. Allergic-type hypersensitivity reactions, including anaphylaxis, are possible. Patients must be closely monitored and carefully observed for any symptoms throughout the infusion period. Patients should be informed of the early signs of hypersensitivity reactions including hives, generalized urticaria, tightness of the chest, wheezing, hypotension, and anaphylaxis. If these symptoms occur during administration, treatment must be discontinued immediately and emergency treatment should be administered.

The anticoagulant effect of drugs that use antithrombin to exert their anticoagulation may be altered when ATryn is added or withdrawn. To avoid excessive or insufficient anticoagulation, coagulation tests suitable for the anticoagulant used (e.g., aPTT and anti-Factor Xa activity) are to be performed regularly, at close intervals, and in particular in the first hours following the start or withdrawal of ATryn. Additionally, patients should be monitored for the occurrence of bleeding or thrombosis in such situations.

The serious adverse reaction that has been reported in clinical studies is hemorrhage (intra-abdominal, hemarthrosis, and post procedural). The most common adverse events reported in clinical trials at a frequency of
≥ 5% are hemorrhage and infusion site reaction.

For more information, please view full Prescribing Information for ATryn.

To report suspected adverse reactions contact rEVO Biologics at 800-610-3776 or the FDA at 800-FDA-1088 or

For more information, please see full Prescribing Information for ATryn.

® ATryn is a registered trademark of rEVO Biologics, Inc.
rEVO Biologics is a registered trademark of LFB S.A.

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