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Generic name: rilonaceptril-ON-a-sept ]
Drug class: Interleukin inhibitors

Medically reviewed by Judith Stewart, BPharm. Last updated on May 1, 2023.

What is Arcalyst?

Arcalyst is used to treat some of the symptoms of rare genetic conditions such as Familial Cold Auto-inflammatory Syndrome (FCAS) or Muckle-Wells Syndrome (MWS).

FCAS and MWS are inflammatory disorders in which the body develops certain symptoms in response to cold, heat, stress, or tiredness. These symptoms often include rash, fever, and joint pain, and eye redness or discomfort. More serious symptoms may include deafness or kidney failure.

Arcalyst may treat or prevent the symptoms of Familial Cold Auto-inflammatory Syndrome (FCAS) or Muckle-Wells Syndrome (MWS) in adults and children at least 12 years old.

Arcalyst is also used to control symptoms of a condition called Deficiency of Interleukin-1 Receptor Antagonist (DIRA), in adults and children who weigh at least 22 pounds (10 kilograms). DIRA is a very rare genetic condition that causes a severe inflammatory reaction during the first days of life and can lead to organ failure throughout the body.

Arcalyst is not a cure for these inherited conditions.

Arcalyst is also used to reduce episodes of recurrent pericarditis (RP) in adults and children at least 12 years old. RP can cause pounding heartbeats, trouble breathing, and severe chest pain spreading to your back or neck.


Serious and sometimes fatal infections may occur during treatment with Arcalyst. Call your doctor right away if you have signs of infection such as: fever, chills, sore throat, flu symptoms, or open sores on your body.

You should not use Arcalyst if you are allergic to rilonacept, or if you have any type of infection.

Before using Arcalyst, tell your doctor if you have an active or chronic infection, a history of tuberculosis or recurrent infections, or high cholesterol or triglycerides. Make sure you are current on all vaccines before you start treatment with Arcalyst.

Tell your doctor about all other medications you use, especially drugs to treat arthritis, psoriasis, Crohn's disease, or ankylosing spondylitis.

Do not receive a "live" vaccine while using Arcalyst. The vaccine may not work as well during this time, and may not fully protect you from disease. Avoid coming into contact with anyone who has recently received a live vaccine. There is a chance that the virus could be passed on to you.

Before taking this medicine

You may not be able to use Arcalyst if you have an active infection.

Tell your doctor if you have any signs of infection (fever, cough, flu symptoms, open sores), or if you have ever had:

  • an active or chronic infection, including HIV;

  • hepatitis B or C;

  • tuberculosis (or if anyone in your household has tuberculosis);

  • a weak immune system (caused by disease or by using certain medicine);

  • diabetes;

  • asthma; or

  • high cholesterol or triglycerides (a type of fat in blood).

Make sure you are current on all vaccines before you start treatment with Arcalyst.

Using Arcalyst may increase your risk of developing certain types of cancer. Talk with your doctor about your specific risk.

Tell your doctor if you are pregnant or breastfeeding.

How is Arcalyst given?

Use Arcalyst exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets.

Arcalyst is injected under the skin once per week. A healthcare provider may teach you how to properly use the medication by yourself.

Your doses may be given in one or two injections at a time, each on a different place on your body.

Arcalyst must be mixed with a liquid (diluent) before using it. When using injections by yourself, be sure you understand how to properly mix and store the medicine.

Use a different place on your stomach, thigh, or upper arm each time you give the injection. Your care provider will show you the best places on your body to inject the medication. Do not inject into the same place two times in a row.

While using Arcalyst, you may need frequent blood tests.

Each vial (bottle) is for one use only. Throw it away after one use, even if there is still medicine left inside.

Use a needle and syringe only once and then place them in a puncture-proof "sharps" container. Follow state or local laws about how to dispose of this container. Keep it out of the reach of children and pets.

Store the unmixed powder medicine in the refrigerator and protected from light. Do not freeze. Keep each vial in the original container until you are ready to mix your medicine.

After mixing Arcalyst with a diluent, store at room temperature and use it within 3 hours. Protect from light.

What happens if I miss a dose?

Call your doctor for instructions if you miss a dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while using Arcalyst?

Do not receive a "live" vaccine while using Arcalyst. Live vaccines include measles, mumps, rubella (MMR), rotavirus, typhoid, yellow fever, varicella (chickenpox), zoster (shingles), and nasal flu (influenza) vaccine.

Ask your doctor before getting a pneumonia vaccine or flu shot while you are using Arcalyst.

Arcalyst side effects

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

You may get infections more easily, even serious or fatal infections. Call your doctor right away if you have signs of infection such as:

  • fever, chills, sore throat;

  • open sores on your body;

  • cough with mucus, feeling short of breath;

  • headache, neck stiffness, increased sensitivity to light, confusion; or

  • chest discomfort, wheezing, dry cough, rapid weight loss.

Also call your doctor at once if you have:

  • bloody, black, or tarry stools;

  • coughing up blood or vomit that looks like coffee grounds;

  • wheezing, chest tightness, trouble breathing;

  • pain or burning when you urinate; or

  • signs of an ear infection - fever, ear pain or full feeling, trouble hearing, drainage from the ear, fussiness in a child.

Common Arcalyst side effects may include:

  • cold symptoms such as stuffy nose, runny nose, sneezing, sore throat;

  • ear infection;

  • muscle or joint pain;

  • rash; or

  • pain, swelling, redness, itching, warmth, blistering, bleeding, bruising, a rash, or a lump where the medicine was injected.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Arcalyst?

Tell your doctor about all your other medicines, especially:

This list is not complete. Other drugs may interact with rilonacept, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Arcalyst only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.