About This Tool

The Orencia Dosing Calculator is a clinical support tool designed for healthcare professionals to determine the appropriate dosage of abatacept for patients with Rheumatoid Arthritis (RA), Psoriatic Arthritis (PsA), or Juvenile Idiopathic Arthritis (JIA). It calculates weight-based intravenous (IV) doses and provides guidance on subcutaneous (SC) administration according to the FDA-approved prescribing information.

Outputs

After inputting patient data, the calculator provides the following key information:

• Calculated Dose: The precise intravenous (IV) dose in milligrams (mg) based on the patient’s body weight, or the fixed subcutaneous (SC) dose.
• Dosing Schedule: Standard administration frequency for induction and maintenance phases (e.g., Weeks 0, 2, 4, then every 4 weeks for IV).
• Administration Route: Confirms the recommendation based on the selected IV or SC route.
• Important Notes: Provides context-specific alerts, such as dosage caps, weight limitations for certain formulations, or details on optional IV loading doses for SC therapy.

How to Use

To ensure accurate results, follow these steps:

1. Select Indication: Choose the appropriate condition from the dropdown menu (Adult RA, Adult PsA, or Pediatric JIA).
2. Enter Patient Weight: Input the patient’s current body weight. Ensure the correct unit (kg or lbs) is selected.
3. Choose Administration Route: Select either Intravenous (IV) Infusion or Subcutaneous (SC) Injection.
4. Specify Loading Dose (if applicable): If initiating SC therapy for an adult, decide whether to include the optional one-time IV loading dose. This option only appears when relevant.
5. Calculate: Click the “Calculate” button to view the recommended dosing regimen.

Dosing Overview

Orencia (abatacept) dosing is based on indication, patient weight, and route of administration.

Adult Rheumatoid Arthritis (RA) & Psoriatic Arthritis (PsA)

Pediatric Juvenile Idiopathic Arthritis (JIA) (≥2 years)

Switching Between Formulations

Patients may be switched between intravenous and subcutaneous administration. When switching from IV to SC therapy, the first subcutaneous dose should be administered instead of the next scheduled intravenous dose. The optional IV loading dose is not required when switching from established IV therapy.

Missed Dose

If a patient misses a weekly subcutaneous injection, they should be instructed to administer the dose as soon as they remember, and then continue with their original weekly schedule. For missed intravenous infusions, the patient should contact their healthcare provider for guidance on rescheduling their next infusion. Do not double the dose to make up for a missed one.

Safety Alerts

FAQ

Frequently Asked Questions

1. Why doesn’t the adult IV dose change with every kilogram of weight?

The approved dosing for adults is tiered into three weight brackets (<60 kg, 60-100 kg, >100 kg) to simplify administration while maintaining efficacy and safety across a range of body sizes.

2. Is the IV loading dose mandatory when starting SC therapy in adults?

No, the single, weight-based IV loading dose is optional. It may be administered at the discretion of the prescribing physician prior to the first weekly subcutaneous injection.

3. What is the maximum IV dose calculated for a JIA patient?

The calculator caps the IV dose for JIA patients at 1000 mg, per the prescribing information, even if their weight exceeds 100 kg (10 mg/kg * 100 kg = 1000 mg).

4. Can I use this calculator for a 5 kg child with JIA?

The calculator will show a warning. Subcutaneous dosing is not recommended for JIA patients weighing less than 10 kg, and IV administration is indicated for patients aged 6 years and older. Dosing in these populations has not been studied.

5. How is the Orencia IV solution prepared?

Orencia for IV infusion is supplied as a lyophilized powder that must be reconstituted and further diluted before administration. The infusion should be administered over 30 minutes. Refer to the full Prescribing Information for detailed instructions.

6. What happens if I enter an indication like psoriatic arthritis and select the SC route?

The tool will correctly show the standard adult subcutaneous dose of 125 mg weekly and present the option to include a one-time IV loading dose.

7. Why is there no loading dose option for JIA patients starting SC therapy?

The optional IV loading dose is only indicated for adult patients with RA or PsA who are initiating subcutaneous therapy. It is not part of the approved dosing regimen for pediatric JIA.

8. Does the calculator account for renal or hepatic impairment?

No. This tool calculates standard doses based on weight and indication only. Dose adjustments for renal or hepatic impairment have not been formally studied. Consult the Prescribing Information and use clinical judgment.

9. Are the subcutaneous JIA doses available in single pre-filled syringes?

Yes, Orencia is available in prefilled syringes corresponding to the recommended JIA doses: 50 mg, 87.5 mg, and 125 mg.

10. Can I switch from lbs to kg after entering a weight?

Yes, the tool allows you to toggle between units. However, it does not automatically convert the entered number. You must re-enter the correct weight value for the newly selected unit before calculating.

References

1. ORENCIA® (abatacept) Prescribing Information. U.S. Food and Drug Administration. Bristol-Myers Squibb Company, Princeton, NJ. [Accessed October 2023]. Available at: FDA.gov
2. ORENCIA® (abatacept) for Healthcare Professionals. Bristol Myers Squibb. [Accessed October 2023]. Available at: OrenciaHCP.com
3. Drugs@FDA: FDA-Approved Drugs. ORENCIA (abatacept). Application Number: 125118. Available at: FDA Drugs@FDA Database
4. Curtis JR, Singh JA. Use of Biologics and Tofacitinib in Rheumatoid Arthritis: American College of Rheumatology Update of 2012 and 2013 Recommendations. Arthritis & Rheumatology. 2015;67(9).