Afstyla (Antihemophilic Factor)

• Allergic reactions may occur. Immediately stop treatment and call your healthcare provider right away if you get a rash or hives, itching, tightness of the chest or throat, difficulty breathing, light-headedness, dizziness, nausea, or decrease in blood pressure.
• Your body may form inhibitors to Factor VIII. An inhibitor is a part of the body's defense system. If you form inhibitors, it may stop this medicine from working properly. The greatest risk of this occurring is in previously untreated patients. Your healthcare provider may need to test your blood for inhibitors from time to time.
• Common side effects are dizziness and allergic reactions.
• These are not the only side effects possible. Tell your healthcare provider about any side effect that bothers you or does not go away.

For intravenous use after reconstitution only.

Dosing Guidelines

• Dose and duration of treatment depend on the severity of the Factor VIII deficiency, the location and extent of bleeding, and the patient's clinical condition.
• Each vial of Afstyla states the actual amount of Factor VIII activity in International Units (IU) as determined by chromogenic assay. One IU corresponds to the activity of Factor VIII contained in 1 milliliter (mL) of normal human plasma.
• Plasma Factor VIII levels can be monitored using either a chromogenic assay or a one-stage clotting assay – routinely used in US clinical laboratories. If the one-stage clotting assay is used, multiply the result by a conversion factor of 2 to determine the patient's Factor VIII activity level.

Calculating Required Dose

The expected in vivo peak increase in Factor VIII level expressed as IU/dL (or % of normal) is estimated using the following formula:

Estimated Increment of Factor VIII (IU/dL or % of normal) = [Total Dose (IU)/body weight (kg)] × 2 (IU/dL per IU/kg)

The dose to achieve a desired in vivo peak increase in Factor VIII level may be calculated using the following formula:

Dose (IU) = body weight (kg) × Desired Factor VIII rise (IU/dL or % of normal) × 0.5 (IU/kg per IU/dL)

• The calculation of the required dose of Factor VIII is based on the empirical finding that 1 IU Factor VIII per kg body weight raises the plasma Factor VIII level by 2 IU/dL.
• The amount of Afstyla to be administered and the frequency of administration should always be oriented to the clinical effectiveness in the individual case.

On-Demand Treatment And Control Of Bleeding Episodes

A guide for dosing Afstyla in the treatment and control of bleeding episodes is provided in Table 1. Consideration should be given to maintaining a Factor VIII activity at or above the target range.

Table 1. Dosing for On-demand Treatment and Control of Bleeding Episodes

Routine Prophylaxis

• Adults and adolescents (≥12 years): The recommended starting regimen is 20 to 50 IU per kg of Afstyla administered 2 to 3 times weekly.
• Children (<12 years): The recommended starting regimen is 30 to 50 IU per kg of Afstyla administered 2 to 3 times weekly. More frequent or higher doses may be required in children <12 years of age to account for the higher clearance in this age group.
• The regimen may be adjusted based on patient response.

Perioperative Management Of Bleeding

A guide for dosing Afstyla during surgery (perioperative management of bleeding) is provided in Table 2. Consideration should be given to maintaining a Factor VIII activity at or above the target range.

Table 2. Target Factor VIII Activity Levels for Perioperative Management of Bleeding

• There are no data with Afstyla use in pregnant women to inform on drug-associated risk.
• There is no information regarding the excretion of Afstyla in human milk, the effect on the breastfed infant, or the effects on milk production.
• The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for Afstyla and any potential adverse effects on the breastfed infant from Afstyla or from the underlying maternal condition.