Arcalyst (Rilonacept) Maintenance Dosing
For CAPS/FCAS/MWS and recurrent pericarditis, adults receive 160 mg once weekly subcutaneously after a 320 mg loading dose, while pediatric patients (12-17 years) receive 2.2 mg/kg weekly (maximum 160 mg) after a 4.4 mg/kg loading dose; for DIRA, both adults and pediatric patients receive 4.4 mg/kg weekly (maximum 320 mg) without dose reduction after loading. 1
Weight-Based Dosing by Indication
CAPS, FCAS, MWS, and Recurrent Pericarditis
Adults:
- Maintenance dose: 160 mg once weekly as a single 2-mL subcutaneous injection 1
- Loading dose: 320 mg delivered as two 160 mg injections on the same day at different sites 1
Pediatric Patients (12-17 years):
- Maintenance dose: 2.2 mg/kg once weekly, up to maximum of 160 mg 1
- Loading dose: 4.4 mg/kg (maximum 320 mg) 1
- Administered as single subcutaneous injection up to 2 mL 1
- These dosing recommendations align with EULAR/ACR 2021 guidelines for IL-1 mediated autoinflammatory diseases 2
DIRA (Deficiency of IL-1 Receptor Antagonist)
Adults and Pediatric Patients ≥10 kg:
- Maintenance dose: 4.4 mg/kg once weekly, up to maximum of 320 mg 1
- No loading dose reduction—same dose used for both loading and maintenance 1
- Administered as one or two subcutaneous injections with maximum 2 mL per injection site 1
- Critical distinction: DIRA requires higher maintenance dosing (4.4 mg/kg) compared to CAPS/MWS (2.2 mg/kg) 1
Maximum Dose Limits
Weekly maximum doses are strictly defined:
- Adults: 320 mg maximum for DIRA; 160 mg maximum for CAPS/MWS/RP 1
- Pediatric patients: Weight-based dosing capped at adult maximum (160 mg for CAPS/MWS/RP; 320 mg for DIRA) 1
- Arcalyst should not be given more frequently than once weekly 1
Missed Dose Management
If a once-weekly dose is missed:
- Administer within 7 days of the missed dose, then resume original schedule 1
- If not administered within 7 days, give the dose and start a new schedule based on that date 1
Administration Specifications
Each dose requires:
- Maximum single-injection volume of 2 mL per site 1
- Doses exceeding 2 mL (>160 mg) require two injections at different sites on the same day 1
- Rotate injection sites (abdomen, thigh, upper arm) 1
- Never inject at sites that are bruised, red, tender, or hard 1
Clinical Efficacy Timeline
Rilonacept demonstrates rapid therapeutic response:
- Median time to pain resolution: 5 days 3
- Median time to CRP normalization: 7-9 days 3, 4
- Long-term treatment (72-96 weeks) maintains symptom control with mean key symptom scores reduced from 2.6 to 0 5
- Annualized recurrence rate on rilonacept: 0.04 events/patient-year versus 4.4 events/patient-year on oral therapies 6
Common Pitfalls
Avoid these dosing errors:
- Do not use CAPS/MWS maintenance dosing (2.2 mg/kg) for DIRA patients—they require 4.4 mg/kg maintenance 1
- Do not exceed once-weekly administration frequency regardless of symptom control 1
- Do not split doses across multiple days; if >160 mg needed, give as two injections same day 1
- Reconstituted solution must be used within 3 hours and protected from light 1