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IL-1α/β and IL-18 Fusion Protein Trap

Rilonacept (IL-1 Trap — Recurrent Pericarditis)

Brand names: Arcalyst

Rilonacept is a subcutaneously injected interleukin-1 blocker (an IL-1 'trap' fusion protein) used in recurrent pericarditis and certain cryopyrin-associated periodic syndromes.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It is a soluble decoy receptor that binds and neutralises interleukin-1 beta (and interleukin-1 alpha), preventing IL-1 from activating its cell-surface receptors and dampening the inflammatory response.

Prescribing in practice

  • By blocking interleukin-1 it increases the risk of serious infection, so it should not be started during active infection and live vaccines should be avoided during treatment.
  • Injection-site reactions are common, and lipid changes have been reported.
  • It should be used under specialist supervision and patients should be up to date with appropriate vaccinations before starting.

Monitoring

Monitor for signs of infection and review lipid profile periodically during treatment.

Counselling the patient

  • Seek medical advice promptly if you develop signs of infection such as fever.
  • Rotate injection sites and report persistent redness or swelling.
  • Do not have live vaccines without checking with your specialist team.

Evidence & guidelines

Use in recurrent pericarditis is supported by the RHAPSODY phase III trial and the product SPC.

Reference: Klein et al. NEJM 2021 (RHAPSODY trial); MHRA Approval Arcalyst 2022; ESC Pericarditis Guidelines 2015; FDA Prescribing Information Arcalyst 2021; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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