About

This Benlysta IV Dosing calculator provides a streamlined method for healthcare professionals to determine patient-specific dosing, administration, and scheduling parameters for belimumab intravenous infusions. By interpreting standard clinical guidelines, it aims to reduce calculation errors and support safe medication practices for patients with systemic lupus erythematosus (SLE) or active lupus nephritis (LN).

Outputs

After entering the patient's weight and treatment start date, the calculator generates a comprehensive dosing and administration plan, including:

• Total Dose (mg): The calculated amount of belimumab required for the infusion, based on the standard 10 mg/kg dosage.
• Volume to Withdraw (mL): The precise volume of reconstituted Benlysta solution (at 80 mg/mL) needed to achieve the total dose.
• Total Infusion Volume (mL): The final volume after the drug is added to a 250 mL bag of 0.9% Sodium Chloride.
• Infusion Rate (mL/hr): The rate required to administer the total infusion volume over the standard 60-minute period.
• Dosing Schedule: Key dates for the first four infusions, covering the induction phase (Weeks 0, 2, 4) and the first maintenance dose (Week 8).

How to use

To use the calculator effectively, please follow these 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) as the unit of measure. The tool will automatically handle the conversion.
3. Select Treatment Start Date: Use the date picker to set the planned date of the first infusion.
4. Calculate: Click the "Calculate Dose" button to generate the complete results.

Dosing overview

The standard intravenous dosage regimen for Benlysta is 10 mg/kg administered over 1 hour. The dosing schedule consists of an induction phase followed by a maintenance phase:

• Induction Dosing: The first three doses are administered at 2-week intervals (Week 0, Week 2, and Week 4).
• Maintenance Dosing: Subsequent doses are administered at 4-week intervals.

The calculated dose should be reconstituted and then diluted in a 250 mL infusion bag of 0.9% Sodium Chloride Injection, USP, prior to administration.

Switching

This calculator is designed exclusively for the intravenous (IV) formulation of Benlysta. It should not be used for the subcutaneous (SC) formulation. If a patient is switching between IV and SC formulations, consult the official prescribing information for guidance on timing and dosing, as the schedules differ. The first SC dose should typically be administered 2 to 4 weeks after the last IV dose.

Missed dose

If a planned maintenance infusion (every 4 weeks) is missed, it should be administered as soon as possible. Thereafter, the patient's dosing schedule should be resumed with 4-week intervals from the date the missed dose was administered. The therapeutic window and clinical context should always be considered when rescheduling doses.

Safety alerts

Benlysta is associated with important safety considerations. Key warnings and precautions include increased risk of serious infections, hypersensitivity reactions including anaphylaxis, depression, and suicidality. It is not recommended in combination with other biologics. This is not a complete list of risks. Always consult the full prescribing information for comprehensive safety data before prescribing or administering Benlysta.

FAQ

What is the final concentration of Benlysta after reconstitution?

After reconstituting either the 120 mg or 400 mg vial with the specified amount of Sterile Water for Injection, the resulting concentration is 80 mg/mL.

Can I use this calculator for the subcutaneous (SC) formulation?

No. This tool is exclusively for the intravenous (IV) infusion of Benlysta. Dosing, administration, and scheduling for the SC formulation are different.

How is the total infusion volume calculated?

The total infusion volume is the sum of the diluent (250 mL of 0.9% NaCl) and the calculated volume of reconstituted Benlysta needed for the patient's dose.

Why is the infusion rate equal to the total infusion volume?

The standard administration time for a Benlysta IV infusion is 1 hour (60 minutes). Therefore, the infusion rate in mL/hr is numerically equal to the total volume in mL (e.g., 255 mL is infused at 255 mL/hr).

What should I do if a patient's weight changes significantly?

Since the Benlysta IV dose is weight-based (10 mg/kg), the dose should be recalculated and adjusted if there is a significant change in the patient's weight to ensure proper dosing.

Is there a maximum dose of Benlysta?

The prescribing information does not specify an absolute maximum dose; however, doses are based on actual body weight. Doses exceeding 1000 mg (for a 100 kg patient) have been studied in clinical trials.

What happens after the 4th dose shown in the schedule?

The calculator displays the induction schedule (Weeks 0, 2, 4) and the first maintenance dose (Week 8). Subsequent maintenance doses should be administered every 4 weeks thereafter.

Does the calculator account for renal or hepatic impairment?

No, the calculator performs a standard weight-based calculation. The prescribing information states that no dosage adjustment is necessary for patients with renal or hepatic impairment, but clinical judgment should always be used.

References

• BENLYSTA® (belimumab) Prescribing Information. GlaxoSmithKline; 2023. Available from: FDA.gov
• GlaxoSmithKline. Benlysta for Healthcare Professionals. Available from: gskpro.com
• European Medicines Agency. Benlysta (belimumab) Summary of Product Characteristics. Available from: ema.europa.eu
• Drugs@FDA: FDA-Approved Drugs. BENLYSTA (belimumab). Application No. 125384. Available from: accessdata.fda.gov