Rilonacept is a dimeric fusion protein consisting of the ligand-binding domains of the extracellular portions of the human interleukin-1 receptor component (IL-1RI) and IL-1 receptor accessory protein (IL-1RAcP) linked in-line to the Fc portion of human IgG1. Rilonacept has a molecular weight of approximately 251 kDa. Rilonacept is expressed in recombinant Chinese hamster ovary (CHO) cells.

ARCALYST (rilonacept) is supplied in single-use, 20-mL glass vials containing a sterile, white to off-white, lyophilized powder. Each vial of ARCALYST (rilonacept) is to be reconstituted with 2.3 mL of Sterile Water for Injection. A volume of up to 2 mL can be withdrawn, which is designed to deliver 160 mg for subcutaneous administration only. The resulting solution is viscous, clear, colorless to pale yellow, and essentially free from particulates. Each vial contains 220 mg rilonacept (80 mg/ 1mL after reconstitution), histidine, arginine, polyethylene glycol 3350, sucrose, and glycine at a pH of 6.5±0.3. No preservatives are present.

What are the possible side effects of rilonacept (Arcalyst)?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Stop using rilonacept and call your doctor at once if you have a serious side effect such as:

  • new signs of infection such as fever, chills, sore throat, flu symptoms, easy bruising or bleeding, or unusual weakness;
  • black, bloody, or tarry stools;
  • coughing up blood or vomit that looks like coffee grounds;
  • fever and chills with headache, neck stiffness, increased sensitivity to light,...

Read All Potential Side Effects and See Pictures of Arcalyst »

Last reviewed on RxList: 8/6/2009
This monograph has been modified to include the generic and brand name in many instances.


Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

Women's Health

Find out what women really need.