ATryn Dosage

2.1 Dose and Schedule

• ATryn dosage 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).
  
• Treatment goal 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.
  
• A different dosing formula is 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 formula for pregnant patients.
  
• A loading dose should be administered 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.
  
• Treatment should be continued until adequate follow-on anticoagulation is established.

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.

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 formula 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.

2.2 Preparation

• Bring vials to room temperature no more than 3 hours prior to reconstitution.
  
• For the 525 IU vial, reconstitute with 3.2 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).

2.3 Administration

• Administer using an infusion set with a 0.22 micron pore-size, in-line filter.
  
• Administer contents of infusion syringes or diluted solution within 24 hours of preparation when stored at room temperature (68-77°F (20-25°C)).
  
• Discard unused product in accordance with local requirements.
  
• Administer ATryn alone without mixing with other agents, with the exception of the medications in Table 3, which demonstrated compatibility with ATryn in an in vitro mixing study2 when co-infused at selected doses and infusion rates in the same IV tubing with 100 IU/mL of ATryn.
  
• Do not co-infuse ATryn in the same IV line with vecuronium or labetalol, since these medications demonstrated IV incompatibility (i.e., precipitation and/or reduction in ATryn activity).