About this Calculator

The Xofigo® (radium Ra 223 dichloride) Dose Calculator provides a patient-specific dose and total injection volume based on body weight. This tool is intended for healthcare professionals to support the standard dosing regimen of Xofigo, which is 55 kBq (1.49 microcurie) per kg of body weight, administered intravenously every 4 weeks for a total of 6 injections.

Outputs Explained

After entering the patient’s weight, the calculator provides the following key outputs for a single administration:

• Total Dose (Activity) in kBq: The primary dosing unit, calculated by multiplying the patient’s weight in kg by the standard 55 kBq/kg dose.
• Total Dose (Activity) in mCi: The same dose converted to millicuries (mCi) for clinicians who use this unit of radioactivity (1 mCi = 37,000 kBq).
• Total Injection Volume in mL: The volume of solution to be drawn for administration, based on the drug concentration of 1,100 kBq/mL as of the preparation date and time.

How to Use the Calculator

To ensure accurate calculations, follow these simple steps:

1. Enter Patient Weight: Input the patient’s current body weight into the designated field.
2. Select Weight Unit: Choose either kilograms (kg) or pounds (lbs). The calculator will automatically convert pounds to kilograms for the dose calculation.
3. Calculate: Click the “Calculate” button to see the results. The tool instantly displays the required dose in both kBq and mCi, along with the total injection volume.

Dosing Overview

The recommended dose and schedule for Xofigo is an intravenous injection of 55 kBq per kilogram of body weight. A complete course of therapy consists of 6 injections, with one injection administered every 4 weeks. The safety and efficacy of more than 6 injections have not been studied. The volume to be administered is calculated based on the patient’s body weight, the radioactive concentration of the product (1,100 kBq/mL), and the decay of radium-223.

Switching Therapies

The decision to initiate, discontinue, or switch from Xofigo to another therapy should be made by a qualified healthcare provider based on a comprehensive clinical assessment. This includes evaluating disease progression, patient performance status, and hematological parameters. This calculator does not provide guidance on switching therapies.

Missed Dose

If a dose of Xofigo is missed, it should be administered as soon as clinically practical. The schedule for subsequent injections should be adjusted to maintain a 4-week interval between doses. Consult the official prescribing information for detailed guidance.

Safety Alerts

Xofigo can cause significant adverse reactions, most notably bone marrow suppression, leading to anemia, neutropenia, leukopenia, and thrombocytopenia. Blood counts must be monitored before every dose. Treatment may need to be delayed or discontinued based on hematological values. As a radiopharmaceutical, Xofigo must be handled with appropriate safety measures to minimize radiation exposure to healthcare personnel and others.

Frequently Asked Questions (FAQ)

What is the standard dose of Xofigo per kilogram?

The standard recommended dose is 55 kBq per kg of body weight.

Can I enter the patient’s weight in pounds (lbs)?

Yes, the tool allows you to select “pounds” as the unit. It automatically converts the weight to kilograms (1 lb = 0.453592 kg) to perform the dose calculation.

What drug concentration is used for the volume calculation?

The calculation assumes a standard concentration of 1,100 kBq/mL (30 microcurie/mL) at the reference date stated on the vial label.

Why are there two different units for the total dose (kBq and mCi)?

Kilobecquerel (kBq) is the SI unit for radioactivity and is standard in many regions. Millicurie (mCi) is also commonly used in clinical practice, particularly in the United States. The tool provides both for convenience.

What are the weight limits for this calculator?

The calculator is validated for weights between 20 kg (approx. 44 lbs) and 300 kg (approx. 661 lbs), which covers the typical range for adult patients.

How many doses are in a complete course of Xofigo treatment?

A full course of treatment consists of 6 intravenous injections, given 4 weeks apart.

Does this calculator account for radioactive decay over time?

No. This tool calculates the dose to be administered based on the vial’s concentration at the reference time. The actual volume to be drawn must be corrected for decay by the administering facility using standard practices for radiopharmaceuticals.

Is this tool a substitute for professional medical judgment?

No. This tool is for informational and educational purposes only. All calculations must be independently verified. Always consult the most current official Prescribing Information for Xofigo before clinical use.

References

• Xofigo (radium Ra 223 dichloride) – U.S. Prescribing Information (FDA)
• Xofigo – European Public Assessment Report (EMA)
• Official Xofigo® U.S. Website for Healthcare Professionals (Bayer)
• NCCN Clinical Practice Guidelines in Oncology (Prostate Cancer) (National Comprehensive Cancer Network)