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ATryn Dosage

Generic name: ANTITHROMBIN ALFA 525[iU] in 1mL
Dosage form: injection, powder, lyophilized, for solution

The information at is not a substitute for medical advice. Always consult your doctor or pharmacist.

For Intravenous Use Only after Reconstitution

Preparation for Administration

  • Bring vials to room temperature no more than 3 hours prior to reconstitution.
  • Reconstitute with 10 mL Sterile Water for Injection [(WFI) not supplied with ATryn] immediately prior to use. Do not shake.
  • For the 1750 IU vial, reconstitute with 10 mL Sterile Water for Injection [(WFI) not supplied with ATryn] immediately prior to use. Do not shake.
  • Do not use solution containing visible particulates or if it is discolored or cloudy.
  • Draw solution from one or more vials into a sterile disposable syringe for intravenous administration or add solution to an infusion bag containing 0.9% sterile sodium chloride for injection (e.g., dilute solution to obtain a concentration of 100 IU/mL).
  • Administer using an infusion set with a 0.22 micron pore-size, in-line filter.
  • Administer contents of infusion syringes or diluted solution within 8 to 12 hours of preparation when stored at room temperature (68-77°F (20-25°C)).
  • Discard unused product in accordance with local requirements.

Recommended Dose and Schedule

  • The dosage of ATryn is to be individualized based on the patient's pre-treatment functional AT activity level (expressed in percent of normal) and body weight (expressed in kilograms) and using therapeutic drug monitoring (Table 1).
  • The goal of treatment is to restore and maintain functional antithrombin (AT) activity levels between 80% - 120% of normal (0.8 - 1.2 IU/mL).
  • Treatment should be initiated prior to delivery or approximately 24 hours prior to surgery to ensure that the plasma antithrombin level is in the target range at that time.
  • Different dosing formulae are used for the treatment of surgical and pregnant patients. Pregnant women who need a surgical procedure other than Cesarean section should be treated according to the dosing formulae for pregnant patients.
  • Administer loading dose as a 15-minute intravenous infusion, immediately followed by a continuous infusion of the maintenance dose.
  • AT activity monitoring and dose adjustments should be made according to Table 2.
  • Continue treatment until adequate follow-on anticoagulation is established.
Table 1: Dosing Formula for Surgical Patients and Pregnant Women
     Loading Dose
  Maintenance Dose
  (100 − baseline AT activity level)
   x Body
  (100 − baseline AT activity level)
   x Body
  (100 − baseline AT activity level)
   x Body
  (100 − baseline AT activity level)
   x Body

AT Activity Monitoring and Dose Adjustment

AT activity monitoring is required for proper treatment. Check AT activity once or twice per day with dose adjustments made according to Table 2.

Table 2: AT Activity Monitoring and Dose Adjustment
  Initial Monitor Time   AT Level   Dose Adjustment   Recheck AT Level
   2 hours after initiation of treatment    < 80%    Increase 30%    2 hours after each dose adjustment
   80% to 120%    None    6 hours after initiation of treatment or dose adjustment  
   > 120%    Decrease 30%    2 hours after each dose adjustment  

As surgery or delivery may rapidly decrease the AT activity levels, check the AT level just after surgery or delivery. If AT activity level is below 80%, an additional bolus dose may be administered to rapidly restore decreased AT activity level. In such instances, the loading dose formulae in Table 1 should be used, utilizing in the calculation the last available AT activity result. Thereafter, restart the maintenance dose at the same rate of infusion as before the bolus.