About This Tool

This section provides supporting clinical information for the Idelvion® Dose Calculator. The tool is designed as an educational resource for licensed healthcare professionals to calculate dosages for patients with Hemophilia B based on the official Prescribing Information. It is not a replacement for clinical judgment, which should always guide final treatment decisions.

Outputs

After entering the required patient and treatment parameters, the calculator provides the following outputs:

• Total Calculated Dose: The precise theoretical dose in International Units (IU) required to achieve the desired Factor IX level, based on the entered patient weight and treatment goal.
• Recommended Vial Combination: A practical combination of available vial strengths (250, 500, 1000, 2000, 3500 IU) that meets or exceeds the calculated dose.
• Total Administered Dose: The final dose in IU based on the sum of the recommended vial strengths. This amount may be slightly higher than the calculated dose to avoid wasting medication.
• Total Volume for Infusion: The total fluid volume in milliliters (mL) required for the infusion, assuming a standard reconstitution volume of 2.5 mL per vial.

How to Use

To use the calculator, follow these steps:

1. Enter Patient Body Weight: Input the patient’s weight and select the appropriate unit (kg or lbs). The tool will automatically convert lbs to kg for the calculation.
2. Select Treatment Regimen: Choose between On-Demand, Perioperative, or Prophylaxis. The required inputs will change based on this selection.
3. Specify Dosing Goal:
   • For On-Demand or Perioperative, enter the desired Factor IX increase as a percentage (%).
   • For Prophylaxis, enter the desired dose in IU/kg.
4. Confirm Available Vials: Select the vial strengths that are available for use. The tool will use only the checked strengths to formulate its recommendation.
5. Calculate: Press the “Calculate Dose” button to view the results.

Dosing Overview

Idelvion® dosing is individualized based on patient weight, clinical scenario, and treatment goals. The calculator uses the following standard formula for on-demand and perioperative settings:

Dose (IU) = Body Weight (kg) × Desired Factor IX Increase (%) × 1.0 IU/kg per IU/dL

For routine prophylaxis, common starting regimens include:

• Standard 7-Day: 35-50 IU/kg once weekly.
• Individualized 14-Day: 75 IU/kg every 14 days for appropriate patients. Dosing intervals can be adjusted based on bleeding phenotype.

Always consult the full Prescribing Information for detailed guidance on dosing for specific bleed severities, surgical procedures, and patient populations.

Switching

When switching a patient from another Factor IX product, the initial Idelvion® dose and frequency should be determined by a healthcare provider based on the patient’s clinical status and previous treatment history. Careful monitoring of Factor IX activity levels and clinical response is recommended during the transition period.

Missed Dose

If a patient misses a scheduled prophylactic dose, they should administer their dose as soon as they remember. They should then resume their regular 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

The use of Idelvion® may be associated with risks, including hypersensitivity reactions (such as anaphylaxis) and the development of neutralising antibodies (inhibitors) to Factor IX. Patients should be monitored for signs of these adverse reactions. This tool does not account for all potential patient-specific factors or contraindications. Refer to the full Prescribing Information for a complete list of warnings, precautions, and adverse reactions.

Frequently Asked Questions (FAQ)

What happens if I enter the patient’s weight in pounds (lbs)?

The calculator automatically converts the weight from lbs to kilograms (kg) using the standard conversion factor (1 kg ≈ 2.20462 lbs) before performing the dose calculation.

How does the calculator determine the recommended vial combination?

The algorithm aims to meet or exceed the calculated dose with minimal waste. It prioritizes using the largest available vials first and then adds a smaller vial if necessary to cover the remaining dose, which may result in rounding up the total administered dose.

What reconstitution volume does the tool assume for the infusion calculation?

The tool assumes a standard reconstitution volume of 2.5 mL of sterile water for injection per vial, as specified in the Prescribing Information for all vial strengths.

Why is the “Total Administered Dose” sometimes higher than the “Total Calculated Dose”?

This occurs because the administered dose is constrained by the available vial strengths. The tool rounds up to the nearest practical combination of vials to ensure the patient receives at least the minimum required dose, preventing under-dosing.

Can I use this calculator if a patient has developed inhibitors?

No. This calculator is intended for patients without inhibitors to Factor IX. Dosing for patients with inhibitors is complex and requires specialized clinical management.

What dosing factor does the tool use for its calculations?

The calculator uses an incremental recovery of 1.0 IU/dL per IU/kg, as per the clinical trial data referenced in the Prescribing Information.

What if I only have certain vial strengths available?

You should uncheck the boxes for the vial strengths you do not have. The tool will then calculate the best combination using only the selected available strengths.

Is this tool a substitute for the official Idelvion® Prescribing Information?

No. This tool is for educational and convenience purposes only. It is not a substitute for clinical judgment or the official, FDA-approved Prescribing Information, which should always be considered the primary source of guidance.

References

1. Idelvion® [Coagulation Factor IX (Recombinant), Albumin Fusion Protein] Full Prescribing Information. U.S. Food and Drug Administration.
2. Idelvion® Official Healthcare Professional Website. CSL Behring.
3. What is Hemophilia? Centers for Disease Control and Prevention (CDC).
4. Guidelines for the Management of Hemophilia. World Federation of Hemophilia.