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Helixate FS (antihemophilic factor (recombinant)) is indicated for the treatment of classical hemophilia (hemophilia A) in which there is a demonstrated deficiency of activity of the plasma clotting factor FVIII. Helixate FS (antihemophilic factor (recombinant)) provides a means of temporarily replacing the missing clotting factor in order to correct or prevent bleeding episodes, or in order to perform emergency or elective surgery in hemophiliacs.
In clinical studies with the predecessor product HELIXATE, some patients who developed inhibitors on study continued to manifest a clinical response when inhibitor titers were less than 10 Bethesda Units (BU) per mL. When an inhibitor is present, the dosage requirement for FVIII is variable. The dosage can be determined only by clinical response, and by monitoring circulating FVIII levels after treatment (see DOSAGE AND ADMINISTRATION). Because Helixate FS (antihemophilic factor (recombinant)) has similar biological activity to HELIXATE it can be used in the same manner.
Helixate FS (antihemophilic factor (recombinant)) does not contain von Willebrand's factor and therefore is not indicated for the treatment of von Willebrand's disease.
DOSAGE AND ADMINISTRATION
Each bottle of Helixate FS (antihemophilic factor (recombinant)) has the rFVIII potency in international units stated on the label based on the one-stage assay methodology. The reconstituted product must be administered within 3 hours after reconstitution.
General Approach To Treatment And Assessment Of Treatment Efficacy
The dosages described below are presented as general guidance. It should be emphasized that the dosage of Helixate FS (antihemophilic factor (recombinant)) required for hemostasis must be individualized according to the needs of the patient, the severity of the deficiency, the severity of the hemorrhage, the presence of inhibitors, and the FVIII level desired. It is often critical to follow the course of therapy with FVIII level assays. The clinical effect of FVIII is the most important element in evaluating the effectiveness of treatment. It may be necessary to administer more FVIII than estimated in order to attain satisfactory clinical results. If the calculated dose fails to attain the expected FVIII levels, or if bleeding is not controlled after administration of the calculated dosage, the presence of a circulating inhibitor in the patient should be suspected. Its presence should be substantiated and the inhibitor level quantitated by appropriate laboratory tests. When an inhibitor is present, the dosage requirement for FVIII could be extremely variable among different patients, and the optimal treatment can be determined only by the clinical response. Some patients with low-titer inhibitors ( < 10 BU) can be successfully treated with FVIII preparations without a resultant anamnestic rise in inhibitor titer.6 FVIII levels and clinical response to treatment must be assessed to insure adequate response. Use of alternative treatment products, such as Factor IX Complex concentrates, Antihemophilic Factor (Porcine), recombinant Factor VIIa or Anti-Inhibitor Coagulant Complex, may be necessary for patients with anamnestic responses to FVIII treatment and/or high-titer inhibitors.
Calculation of Dosage
The in vivo percent elevation in FVIII level can be estimated by multiplying the dose of Helixate FS (antihemophilic factor (recombinant)) per kilogram of body weight (IU/kg) by 2% per IU per kg. This method of calculation is based on clinical findings with the use of plasma-derived and recombinant AHF products7-9 and is illustrated in the following examples:
|Expected % factor VIII increase =||# units administered x 2%/IU/kg|
|body weight (kg)|
|Example for a 70 kg adult: =||1400 IU x 2%/IU/kg||= 40%|
|Dosage required (IU) =||body weight (kg) x desired % FVIII increase|
|Example for a 15 kg child: =||15 kg x 100%||= 750 IU required|
The dosage necessary to achieve hemostasis depends upon the type and severity of the bleeding episode, according to the following general guidelines:
|Hemorrhagic event||Therapeutically necessary plasma level of FVIII activity||Dosage necessary to maintain the therapeutic plasma level|
|Minor hemorrhage (superficial, early hemorrhages, hemorrhages into joints)||20–40%||10–20 IU per kg Repeat dose if evidence of further bleeding.|
|Moderate to major hemorrhage (hemorrhages into muscles, hemorrhages into the oral cavity, definite hemarthroses, known trauma)||30–60%||15–30 IU per kg Repeat one dose at 12–24 hours if needed.|
|Surgery (minor surgical procedures)|
|Major to life-threatening hemorrhage (intracranial, intraabdominal or intrathoracic hemorrhages, gastrointestinal bleeding, central nervous system bleeding, bleeding in the retropharyngeal or retroperitoneal spaces, or iliopsoas sheath)||80–100%||Initial dose 40–50 IU per kg Repeat dose 20–25 IU per kg every 8–12 hours.|
Major surgical procedures
|~100%||Preoperative dose 50 IU/kg
Verify ~100% activity prior to surgery.
Repeat as necessary after 6 to 12 hours initially, and for 10 to 14 days until healing is complete.
AHF concentrates may also be administered on a regular schedule for prophylaxis of bleeding, as reported by Nilsson et al.10
Instructions for Use
Reconstitution and product administration must be done with caution. Percutaneous puncture with a needle contaminated with blood can transmit infectious viruses including HIV (AIDS) and hepatitis. Obtain immediate medical attention if injury occurs. Place needles in a sharps container after single use. Discard all equipment, including any reconstituted Helixate® FS Antihemophilic Factor (Recombinant) product, in accordance with biohazard procedures.
Always wash your hands before performing the following procedures:
- Warm the unopened diluent and the concentrate to a temperature not to exceed 37°C, 99°F.
- Place the product vial, diluent vial and Mix2Vial™ on a flat surface.
- Ensure product and diluent vial flip caps are removed and the stoppers are treated with an aseptic solution and allowed to dry prior to opening the Mix2Vial package.
- Open the Mix2Vial package by peeling away the lid (Fig. 1). Leave the Mix2Vial in the clear package. Place the diluent vial on an even surface and hold the vial tight. Grip the Mix2Vial together with the package and snap the blue end onto the diluent stopper (Fig. 2).
- Carefully remove the clear package from the Mix2Vial set. Make sure that you only pull up the package and not the Mix2Vial set (Fig. 3).
- With the product vial firmly on a surface, invert the diluent vial with the set attached and snap the transparent adapter onto the product vial stopper (Fig. 4). The diluent will automatically transfer into the product vial.
- With the diluent and product vial still attached, gently swirl the product vial to ensure the product is fully dissolved (Fig. 5). Do not shake vial.
- With one hand grasp the product-side of the Mix2Vial set and with the other hand grasp the blue diluent-side of the Mix2Vial set and unscrew the set into two pieces (Fig. 6).
- Draw air into an empty, sterile syringe. While the product vial is upright, screw the syringe to the Mix2Vial set. Inject air into the product vial. While keeping the syringe plunger pressed, invert the system upside down and draw the concentrate into the syringe by pulling the plunger back slowly (Fig. 7).
- Now that the concentrate has been transferred into the syringe, firmly grasp the barrel of the syringe (keeping the syringe plunger facing down) and unscrew the syringe from the Mix2Vial set (Fig. 8). Attach the syringe to an administration set made with microbore tubing. Use of other administration sets without microbore tubing may result in a larger retention of the solution within the administration set.
- If the same patient is to receive more than one bottle, the contents of two bottles may be drawn into the same syringe through a separate unused Mix2Vial set before attaching the vein needle.
- Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.
Rate of Administration
The rate of administration should be adapted to the response of the individual patient, but administration of the entire dose in 5 to 10 minutes or less is well tolerated.
Helixate® FS Antihemophilic Factor (Recombinant) is supplied in the following single use bottles. A suitable volume of Sterile Water for Injection, USP and Mix2Vial™ filter transfer set are provided. The actual potency is printed on the label and the carton.
|NDC Number||Approximate FVIII Activity (IU)||Dosage||Diluent (mL)|
Helixate FS (antihemophilic factor (recombinant)) stored in a refrigerator at 2–8°C (36–46°F) is stable for the period indicated by the expiration date on the label. Within this period Helixate FS (antihemophilic factor (recombinant)) may be stored at room temperature, not to exceed 25°C (77°F), for up to 3 months, such as in home treatment situations. Do not freeze. Do not use beyond the expiration date indicated on the bottle. Protect from extreme exposure to light and store the lyophilized powder in the carton prior to use.
7. Abildgaard CF, Simone JV, Corrigan JJ, et al: Treatment of hemophilia with glycine-precipitated Factor VIII. N Engl J Med 275(9):471–5, 1966.
8. Schwartz RS, Abildgaard CF, Aledort LM, et al: Human recombinant DNA-derived antihemophilic factor (factor VIII) in the treatment of hemophilia A. Recombinant Factor VIII Study Group. N Engl J Med 323(26):1800-5, 1990.
9. White GC 2nd, Courter S, Bray GL, et al: A multicenter study of recombinant factor VIII (Recombinate) in previously treated patients with hemophilia A. The Recombinate Previously Treated Patient Study Group. Thromb Haemost 77(4):660-667, 1997.
10. Nilsson IM, Berntorp E, Löfqvist T, et al: Twenty-five years' experience of prophylactic treatment in severe haemophilia A and B. J Intern Med 232(1):25–32, 1992.
Product Website: www.hemophiliamoms.com. Manufactured by: Bayer HealthCare LLC, Tarrytown, NY 10591, USA. Distributed by: CSL Behring LLC, Kankakee, IL 60901 USA. Revised July, 2007. FDA Rev date: July 2007This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 1/30/2009
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