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Arcalyst

rilonacept

Used for Autoinflammatory Syndromes

Arcalyst (rilonacept) is a prescription medication that's used to treat adults and children with certain rare inflammatory conditions, including cryopyrin-associated periodic syndromes (CAPS), deficiency of interleukin-1 receptor antagonist (DIRA), and recurrent pericarditis (RP). It's given as an injection under the skin once a week. The medication is approved for use in adults and children 12 years and older. Common side effects include injection site reactions and upper respiratory tract infections.

Reviewed by:

Ally Tsai, PharmD

Daisy Chau, PharmD

Last reviewed on May 16, 2025

Basics Side effects Pros & cons Pharmacist tips FAQs Warnings Dosage Alternatives Prices Medicare

What is Arcalyst (rilonacept)?

What is Arcalyst (rilonacept) used for?

Treatment of cryopyrin-associated periodic syndromes (CAPS), including familial cold autoinflammatory syndrome (FCAS) and Muckle-wells Syndrome (MWS)
Maintenance of deficiency of interleukin-1 receptor antagonist (DIRA)
Treatment and prevention of recurrent pericarditis (RP)

How Arcalyst (rilonacept) works

Arcalyst (rilonacept) is an interleukin-blocker. It works by blocking interleukin-1 (IL-1), a protein in the body that causes inflammation. By stopping IL-1, Arcalyst (rilonacept) helps lower inflammation and manage symptoms of certain inflammatory conditions.

Drug Facts

Common BrandsArcalyst

Drug ClassInterleukin-1 blocker

Controlled Substance ClassificationNot a controlled medication

Generic StatusNo lower-cost generic available

AvailabilityPrescription only

What are the side effects of Arcalyst (rilonacept)?

The following side effects may get better over time as your body gets used to the medication. Let your healthcare provider know immediately if you continue to experience these symptoms or if they worsen over time.

Common Side Effects

Pain, itching, and swelling around the injection site (48%)
Upper respiratory tract infection (26%)

Side effects listed above are for people with CAPS. Similar side effects were reported in people with DIRA and RP.

Other Side Effects

Cough
Feeling numb
Nausea
Diarrhea
Urinary tract infection (UTI)
Ear infection
Rash
Sore throat

Serious Side Effects

Contact your healthcare provider immediately if you experience any of the following.

Serious infections: fever, cough, chills, sore throat, runny or stuffy nose, body aches, open sores, feeling tired
Allergic reaction: rash, swollen face, trouble breathing

Source: DailyMed

The following side effects have also been reported

Side effects that you should report to your care team as soon as possible:

Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
Infection—fever, chills, cough, sore throat, wounds that don't heal, pain or trouble when passing urine, general feeling of discomfort or being unwell

Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):

Cough
Diarrhea
Nausea
Numbness, decrease in sense of touch or sensation
Pain, redness, or irritation at injection site
Sinus pain or pressure around the face or forehead

Pros and cons of Arcalyst (rilonacept)

Pros

Only injected once a week

Can be used to treat adults and children

The first and only FDA-approved medication for RP

Cons

Commonly causes injection-site reactions

Carries a risk of serious infections

Must prepare the medication before using

Pharmacist tips for Arcalyst (rilonacept)

Don't give yourself or your child Arcalyst (rilonacept) until you’ve learned how to prepare and inject it correctly. Your healthcare team will show you how to do your first dose. You can also visit this website for step-by-step instructions.

Arcalyst (rilonacept) is injected under the skin on the stomach or thighs. Avoid the area within 2 inches of your belly button. If you're giving the injection to someone else, you can also use the underside of their upper arms.

If your dose includes two injections of Arcalyst (rilonacept) on the same day, use different spots on the body. This helps avoid skin irritation.

Always inject Arcalyst (rilonacept) into skin that is clean and healthy. Don’t inject into areas that are red, bruised, sore, or hard. Change injection spots each time to protect your skin.

Only use sterile water, syringes, or needles provided by your pharmacy. Don't share or reuse needles or syringes to prevent possible infections. Throw away your supplies in a sharps container after each use.

Avoid live vaccines while taking Arcalyst (rilonacept). Talk to your healthcare team about which vaccines are safe.

Call your prescriber if you or your child get a fever, sore throat, cough, or chills while taking Arcalyst (rilonacept). These could be signs of a serious infection.

Some medications, like Enbrel (etanercept) or Humira (adalimumab), can interact with Arcalyst (rilonacept) and increase your risk of infection. Tell your care team about all the medications and supplements you take so they can make sure everything is safe to take together.

Store Arcalyst (rilonacept) in the refrigerator before mixing. Keep it in the original container to protect it from light.

After mixing Arcalyst (rilonacept) with sterile water, keep the mixture at room temperature. Make sure to use the medication within 3 hours.

Frequently asked questions about Arcalyst (rilonacept)

Does Arcalyst (rilonacept) cause weight gain?

Weight gain isn't a common side effect of Arcalyst (rilonacept). But you might also take corticosteroids with this medication, and those can cause weight gain. Everyone reacts differently to treatment, so talk to your prescriber if you're worried about any changes in your weight.

Is Arcalyst (rilonacept) a monoclonal antibody?

No. Arcalyst (rilonacept) is a fusion protein. Monoclonal antibodies, like Humira (adalimumab), are lab-made antibodies that attach to specific proteins in your body. Fusion proteins, like Arcalyst (rilonacept), are made by joining parts of different proteins.

What's the difference between Arcalyst (rilonacept) versus Kineret?

Arcalyst (rilonacept) and Kineret (anakinra) both help block the IL-1 protein to lower inflammation, but they differ slightly in what they're FDA approved to treat. Both can be used for CAPS and DIRA, but Kineret (anakinra) is also approved for rheumatoid arthritis (RA). Arcalyst (rilonacept) is usually injected once a week, while Kineret (anakinra) is injected once a day. Talk to your healthcare team if you have questions about comparing the two medications.

How long can you take Arcalyst (rilonacept)?

Use Arcalyst (rilonacept) as directed by your healthcare team, usually for as long as it continues to work for you and you don’t have serious side effects. In clinical studies, people have used this medication from weeks to years to keep their condition under control. Your prescriber will regularly check how you’re doing and decide if you should keep taking it or make any changes to your treatment.

Can Arcalyst (rilonacept) cause joint pain?

Joint pain isn't a common side effect of Arcalyst (rilonacept). Instead, this medication is used to treat joint pain in inflammatory conditions like CAPS. If you develop joint pain while using Arcalyst (rilonacept), talk to your healthcare team right away. It can be a flare up of your inflammatory condition.

How long has Arcalyst (rilonacept) been around?

Arcalyst (rilonacept) was originally FDA approved in February 2008 to treat CAPS. It was later approved for the maintenance of DIRA in December 2020, and for the treatment and prevention of RP in April 2021.

Is Arcalyst (rilonacept) safe in pregnancy?

Arcalyst (rilonacept) hasn’t been studied in human pregnancies. But in animal studies, some baby monkeys were harmed when their mothers were given this medication during pregnancy. While animal results don't always predict what will happen in people, there's a chance Arcalyst (rilonacept) could cause serious side effects to unborn babies. Talk with your healthcare team to discuss the benefits and risks of taking this medication during pregnancy.

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What are the risks and warnings for Arcalyst (rilonacept)?

Arcalyst (rilonacept) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.

Serious infections

Risk factors: Current, long-term, or recurrent infection | History of HIV, hepatitis B, or hepatitis C | History of asthma | History of tuberculosis (TB) | History of diabetes or other immune system problems | Taking other medications that can weaken the immune system

Arcalyst (rilonacept) can lower your body's ability to fight off infections. Serious infections — like bronchitis, TB, and meningitis, — have happened in people taking this medication. You shouldn’t take certain medications, like corticosteroids or TNF blockers, with Arcalyst (rilonacept) because they can raise your risk of serious infections.

Don't use Arcalyst (rilonacept) if you have a current infection, a long-term infection, or infections that keep coming back. This medication can make these infections worse. Call your healthcare team right away if you notice signs or symptoms of an infection like fever, cough, chills, sore throat, runny or stuffy nose, body aches, open sores, or feeling tired.

Possible risk of cancer

It’s not clear whether taking Arcalyst (rilonacept) can put you at risk for cancer. Some other medications that affect the immune system, like Enbrel (etanercept), have been linked to a higher risk of certain cancers. If you're worried, talk to your prescriber to see if Arcalyst (rilonacept) is the right choice for you.

Higher cholesterol and triglycerides levels

Arcalyst (rilonacept) can cause your cholesterol and triglycerides (fats) levels to go up. Your prescriber might check these levels during treatment. If they're too high, they might recommend treatment to help manage your heart health.

Interaction with vaccines

Risk factors: Receiving live vaccines

If you’re taking Arcalyst (rilonacept), you should avoid getting live vaccines, since there’s not enough information about the risk of spreading infection. Vaccines might also not work as well while you’re taking Arcalyst (rilonacept) because it can affect how your immune system responds.

Before starting Arcalyst (rilonacept), your prescriber might recommend that you get all your routine vaccines, including the pneumococcal and inactivated flu vaccines. This helps protect you from infections before your immune system is affected by treatment.

Arcalyst (rilonacept) dosage forms

Typical dosing for Arcalyst (rilonacept)

Arcalyst (rilonacept) needs to be mixed with sterile water before injection.

Adults

CAPS and RP: The starting dose is two separate 160 mg injections given under the skin in two different spots on your body on the same day. After that, you'll inject one 160 mg injection once a week.
DIRA: The typical dose is two separate 160 mg injections given under the skin, once a week.

Children: The dose will depend on the child’s weight.

CAPS and RP (ages 12 to 17): The starting dose is 4.4 mg/kg injected under the skin. After that, your pediatrician will lower the dose to 2.2 mg/kg under the skin once a week.
DIRA (weighing at least 10 kg or 22 lbs): The typical dose is 4.4 mg/kg injected under the skin once a week.