About BeneFIX® Dosing

The BeneFIX® Dose Calculator is a clinical support tool for healthcare professionals to estimate the required dosage of BeneFIX® [Coagulation Factor IX (Recombinant)] for patients with Hemophilia B. This guide provides an overview of the calculator’s functions, the dosing principles it employs, and other relevant clinical information to support treatment decisions. It is not a substitute for clinical judgment or the full Prescribing Information.

Calculator Outputs

After entering the required patient data, the tool provides a clear summary of the dosing requirements:

• Calculated Dose Required: The precise dose in International Units (IU) needed to achieve the desired Factor IX increase, based on the approved formula.
• Recommended Vials: A practical combination of available BeneFIX® vial sizes (e.g., 3000, 2000, 1000, 500, 250 IU) to prepare the required dose.
• Total Dose from Vials: The total IU available from the recommended vial combination. This amount may be slightly higher than the calculated dose to ensure the minimum required dose is met using available vial strengths.

How to Use the Calculator

The calculation process requires three simple steps:

1. Enter Patient Weight: Input the patient’s body weight and select the appropriate unit of measurement (kg or lbs). The calculator automatically converts lbs to kg for the formula.
2. Select Treatment Indication: Choose the clinical scenario from the dropdown menu, such as routine prophylaxis or a minor, moderate, or major bleeding episode.
3. Confirm Desired Factor IX Increase: The tool pre-populates the target Factor IX increase percentage based on the selected indication. This value can be manually adjusted by the clinician to align with specific patient needs or clinical judgment.

Dosing Overview

The dose of BeneFIX® is individualized based on patient weight, the severity of hemorrhage, and the desired target Factor IX level. The calculator uses the following standard formula from the Prescribing Information:

Dose (IU) = Body Weight (kg) × Desired Factor IX Increase (%) × 1.2 IU/kg per IU/dL

The frequency and duration of administration depend on the clinical indication. For major bleeding events or surgery, subsequent infusions may be needed every 8 to 24 hours to maintain adequate hemostasis.

Switching Treatment

Patients switching to BeneFIX® from another Factor IX product should be managed under the supervision of a physician experienced in hemophilia care. Dosing adjustments may be necessary, and patients should be monitored for the development of Factor IX inhibitors.

Missed Dose

If a patient misses a scheduled prophylactic dose, they should administer the dose as soon as they remember and then resume their regular infusion schedule. Patients should be instructed not to administer a double dose to make up for a missed one and to contact their healthcare provider for guidance.

Safety Alerts

Frequently Asked Questions (FAQ)

What is the factor of 1.2 in the BeneFIX® dose formula?

The value of 1.2 (IU/kg per IU/dL) is the reciprocal of the observed recovery. It is a pharmacokinetic constant used to estimate the dose required to achieve a specific circulating level of Factor IX.

How does the calculator choose the vial combination?

The tool uses an algorithm to find an efficient combination of available vial sizes. It typically starts with the largest vials to meet the majority of the dose and then adds smaller vials as needed to reach the calculated target. If the calculated dose falls between vial combinations, it rounds up to ensure the patient receives at least the minimum required dose.

Why is the ‘Total Dose from Vials’ sometimes higher than the ‘Calculated Dose’?

This occurs because the dose must be constituted from fixed vial sizes. The calculator selects the combination that meets or slightly exceeds the calculated requirement to ensure therapeutic targets are met without unnecessary waste.

Can I use this calculator for other Factor IX products?

No. This calculator is specifically designed for BeneFIX®. Other Factor IX products may have different pharmacokinetic properties (e.g., recovery and half-life), and their dosing should be guided by their respective Prescribing Information.

What are the available vial sizes for BeneFIX® used in the calculation?

The calculator uses the following nominal vial strengths: 250, 500, 1000, 2000, and 3000 IU.

Does the calculator account for a patient’s current Factor IX level?

The calculator determines the dose needed for a desired increase in Factor IX levels (e.g., an increase of 30%). It does not require the patient’s baseline level as an input, as the formula is based on achieving a target percentage increase from baseline.

Is this calculator suitable for pediatric patients?

The dosing formula is based on body weight and is applicable to pediatric patients. However, all treatment decisions for pediatric patients must be made by a qualified healthcare professional based on a full clinical evaluation.

What should I do if the calculator output is not showing?

Ensure you have entered a valid, positive number for patient weight and that the “Desired Factor IX Increase” field contains a reasonable value. If issues persist, refer to the manual dosing formula and the full Prescribing Information.

References

1. BeneFIX® [Coagulation Factor IX (Recombinant)] Full Prescribing Information. U.S. Food and Drug Administration.
2. BeneFIX® Official Product Website. Pfizer Inc.
3. World Federation of Hemophilia. Clinical Guidelines and Resources.
4. Hemophilia B (Factor IX Deficiency) Information. Centers for Disease Control and Prevention (CDC).