About This Guide

This information serves as a companion guide to the Renflexis (infliximab-abda) Dosing Calculator calculator. It provides context on the calculator’s inputs, outputs, and the underlying dosing principles based on the FDA-approved Prescribing Information. This guide is for informational purposes and should not replace clinical judgment.

Understanding the Calculator Outputs

After entering the patient’s information and clicking “Calculate,” the tool provides four key results based on a standard 250 mL 0.9% Sodium Chloride infusion bag:

• Total Dose (mg): The precise dose calculated by multiplying the patient’s weight in kg by the indication-specific dose (e.g., 5 mg/kg).
• Number of Vials (100 mg): The number of 100 mg Renflexis vials required. This is calculated by dividing the total dose by 100 and rounding up to the nearest whole number.
• Total Volume to Withdraw (mL): The total volume of reconstituted drug (at 10 mg/mL) to be withdrawn from the vials for administration.
• Total Infusion Volume (mL): The final volume after adding the withdrawn drug volume to the 250 mL saline bag.

How to Use the Calculator

Follow these simple steps to calculate a patient-specific dose:

1. Enter Patient Weight: Input the patient’s weight and select the correct unit (kg or lbs). The calculator automatically converts lbs to kg for the calculation.
2. Select Indication: Choose the appropriate FDA-approved indication from the dropdown menu. This determines the mg/kg dose and maintenance schedule.
3. Choose Dose Type: Select either Induction Dose (for the initial doses at Weeks 0, 2, and 6) or Maintenance Dose.
4. Calculate: Click the “Calculate” button to see the detailed dosing results and administration guidance.

Dosing Overview

Renflexis dosing is weight-based and varies by indication, primarily in the initial mg/kg dose and the maintenance interval. The induction phase is consistent for most listed indications, occurring at Weeks 0, 2, and 6.

Note: For some conditions like Rheumatoid Arthritis or Crohn’s Disease, dose escalation or shortening of the dosing interval may be considered for patients with an incomplete response, as per the official Prescribing Information.

Switching to Renflexis

The decision to switch a patient from another biologic (including reference infliximab) to Renflexis should be made by an experienced healthcare provider. Consult the full Prescribing Information for any specific guidance related to transitioning patients.

Guidance for a Missed Dose

If a patient misses a scheduled infusion, they should contact their healthcare provider immediately to reschedule. The subsequent maintenance schedule should be adjusted based on the timing of the administered dose. Do not administer a double dose to make up for a missed one.

Safety Alerts

This calculator does not screen for contraindications or warnings. Renflexis administration carries risks that must be managed by a qualified healthcare professional.

Frequently Asked Questions (FAQ)

How does the calculator determine the number of vials?

It calculates the total dose in mg and divides it by 100 (the strength per vial). Because partial vials cannot be used, the result is always rounded up to the next whole number to ensure the full dose can be prepared.

Why is the dose for Rheumatoid Arthritis different?

The approved starting dose for Rheumatoid Arthritis is 3 mg/kg, whereas it is 5 mg/kg for most other indications. The calculator reflects this difference based on the selected indication.

Why is the maintenance schedule for Ankylosing Spondylitis every 6 weeks?

The approved maintenance schedule for Ankylosing Spondylitis is every 6 weeks following the induction phase, which is more frequent than the every 8-week schedule for most other conditions. The calculator’s “Dose Schedule” information reflects this.

Does this tool account for dose escalation?

No. The calculator computes the standard, approved starting doses. Dose escalation (e.g., to 10 mg/kg for Crohn’s Disease or adjusting the frequency) is a clinical decision based on patient response and must be determined by the prescribing physician.

What reconstitution assumptions are made?

The calculator assumes each 100 mg vial is reconstituted with 10 mL of Sterile Water for Injection, USP, to yield a final concentration of 10 mg/mL, as per the Prescribing Information.

Can I use this calculator for biosimilars other than Renflexis?

This tool is specifically based on the Renflexis Prescribing Information. While other infliximab biosimilars may have similar dosing, you must always consult the specific Prescribing Information for the product being administered.

What is the “Total Infusion Volume”?

This is the final volume in the IV bag, which consists of the standard 250 mL of 0.9% Sodium Chloride plus the volume of reconstituted Renflexis that was added to it.

Does this calculator work for pediatric patients?

Yes, for the approved pediatric indications shown in the dropdown menu: Crohn’s Disease and Ulcerative Colitis in patients aged 6 years and older. It should not be used for other conditions in pediatric patients or for any patient younger than 6.

References

This information is based on established clinical guidelines and official product labeling. For complete and up-to-date details, consult these primary sources:

1. RENFLEXIS® (infliximab-abda) Prescribing Information. Organon LLC. Revised: 05/2023.
2. FDA Label for RENFLEXIS (infliximab-abda). U.S. Food and Drug Administration.
3. Renflexis Official Healthcare Professional Site. Organon.
4. Lichtenstein, G. R., et al. (2018). ACG Clinical Guideline: Management of Crohn’s Disease in Adults. The American Journal of Gastroenterology, 113(4), 481-517.