ARCALYST
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ARCALYST (ARCALYST).
Interleukin-1 (IL-1) receptor antagonist; binds to IL-1 receptor, blocking IL-1α and IL-1β activity.
| Metabolism | Metabolized via renal degradation; not metabolized by CYP450 enzymes. |
| Excretion | ARCALYST (rilonacept) is not metabolized. Elimination occurs via proteolytic degradation into small peptides and amino acids. Renal excretion of intact drug is negligible. |
| Half-life | Terminal half-life is approximately 8.6 days (range 7-10 days), supporting a once-weekly subcutaneous dosing regimen. |
| Protein binding | Rilonacept is a dimeric fusion protein; specific protein binding data not available. As a large protein, it does not bind to serum proteins in a classic manner; distribution is primarily in plasma and interstitial fluid. |
| Volume of Distribution | Volume of distribution is approximately 5.2 L (based on a 70 kg adult, ~0.074 L/kg), indicating limited extravascular distribution, consistent with a large protein. |
| Bioavailability | Subcutaneous: Estimated absolute bioavailability is approximately 85% (range 70-100%). |
| Onset of Action | Subcutaneous administration: Clinical improvement in symptoms (e.g., reduction in flares) can be observed within a few days to 1 week after the first dose. |
| Duration of Action | Sustained suppression of IL-1 activity persists throughout the 1-week dosing interval. Once-weekly dosing maintains therapeutic levels; missed doses may lead to return of symptoms within 1-2 weeks. |
320 mg subcutaneously every 2 weeks, or 200 mg subcutaneously every week for patients who do not achieve an adequate response to the every-2-week regimen.
| Dosage form | VIAL |
| Renal impairment | For GFR < 30 mL/min/1.73 m2, reduce dose to 200 mg every 2 weeks; for GFR ≥ 30 mL/min/1.73 m2, no adjustment. |
| Liver impairment | No formal studies in hepatic impairment; no specific recommendations for Child-Pugh classes. Use with caution. |
| Pediatric use | For CAPS: children ≥ 12 years weight ≥ 40 kg: 160 mg subcutaneously every 2 weeks; for children ≥ 12 years weight < 40 kg: 2 mg/kg every 2 weeks, maximum 160 mg. For recurrent pericarditis: not established in pediatric patients. |
| Geriatric use | No specific dose adjustment for elderly; monitor renal function as GFR declines with age. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ARCALYST (ARCALYST).
| Breastfeeding | Unknown if excreted in human milk. No data on M/P ratio or effects on breastfed infant. Weigh benefits of breastfeeding against potential risk to infant. |
| Teratogenic Risk | Animal studies show no evidence of teratogenicity or fetal harm at doses up to 100 mg/kg (approximately 10 times the human dose). No adequate human studies in pregnant women; risk cannot be ruled out. Use during pregnancy only if clearly needed. |
| Fetal Monitoring |
■ FDA Black Box Warning
Increased risk of serious infections due to IL-1 blockade; treatment should not be initiated during active infections.
| Serious Effects |
["Hypersensitivity to anakinra or any component of the formulation","Active infections"]
| Precautions | ["Serious infections (including tuberculosis, invasive fungal infections, and other opportunistic infections)","Hypersensitivity reactions (including anaphylaxis)","Immunosuppression (live vaccines should be avoided)","Neutropenia (monitor neutrophil counts)"] |
| Food/Dietary | No known food interactions. |
| Clinical Pearls |
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| Monitor for maternal infections, injection site reactions, and hypersensitivity. Fetal monitoring per standard obstetric care; no specific fetal monitoring required. |
| Fertility Effects | No human data on fertility effects. Animal studies showed no impairment of fertility at doses up to 100 mg/kg. Likely minimal impact on fertility. |
| ARCALYST (rilonacept) is an IL-1 trap approved for Cryopyrin-Associated Periodic Syndromes (CAPS) and recurrent pericarditis. Monitor for injection site reactions; premedicate with antihistamines or NSAIDs if needed. Do not administer live vaccines during therapy. Contraindicated in active or serious infections. Consider tuberculosis screening before initiation. Drug levels may increase with concurrent CYP450 substrates due to IL-1 inhibition of CYP enzymes. |
| Patient Advice | ARCALYST is injected subcutaneously once weekly, typically 320 mg loading dose followed by 160 mg weekly. · Store vials in refrigerator at 2-8°C (36-46°F); do not freeze or shake. · Rotate injection sites (abdomen, thigh, upper arm) and avoid areas with bruises or scars. · Report signs of infection (fever, chills, cough) or allergic reactions (rash, difficulty breathing). · Do not receive live vaccines (e.g., MMR, varicella, nasal flu) during treatment. |