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Generic name: siltuximab
Drug class: Interleukin inhibitors

Medically reviewed by  A Ras MD.

What is Sylvant used for?

Sylvant is a prescription medicine that is used to treat multicentric Castleman’s Disease (MCD).


Siltuximab is a human-mouse chimeric monoclonal antibody that binds human interleukin-6 (IL-6) and is produced by Chinese hamster ovary cells.

SYLVANT (siltuximab) for injection is supplied as a sterile, white, preservative free, lyophilized powder in single-dose vials.

Each SYLVANT 100 mg single-dose vial contains 100 mg siltuximab, 3.7 mg L-histidine (from L-histidine and L-histidine monohydrochloride monohydrate), 0.8 mg polysorbate 80, and 169 mg sucrose.

Each SYLVANT 400 mg single-dose vial contains 400 mg siltuximab, 14.9 mg L-histidine (from L-histidine and L-histidine monohydrochloride monohydrate), 3.2 mg polysorbate 80, and 677 mg sucrose.

Following reconstitution with Sterile Water for Injection, USP (per section 2.2), the resulting pH is approximately 5.2. The resulting solution contains 20 mg/mL siltuximab to be administered by intravenous infusion following dilution

Mechanism of Action

Siltuximab binds human IL-6 and prevents the binding of IL-6 to both soluble and membrane-bound IL-6 receptors. IL-6 has been shown to be involved in diverse normal physiologic processes such as induction of immunoglobulin secretion. Overproduction of IL-6 has been linked to systemic manifestations in patients with MCD.

Before taking Sylvant, tell your doctor:

  • If you are allergic to Sylvant; any part of this medicine; or any other drugs, foods, or substances. Tell your doctor about the allergy and what signs you had.
  • If you have an infection.

This is not a list of all drugs or health problems that interact with this medicine.

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take Sylvant with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some things I need to know or do while I take Sylvant?

  • Tell all of your health care providers that you take Sylvant. This includes your doctors, nurses, pharmacists, and dentists.
  • You may have more chance of getting an infection. Wash hands often. Stay away from people with infections, colds, or flu.
  • Talk with your doctor before getting any vaccines. Use of some vaccines with Sylvant may either raise the chance of an infection or make the vaccine not work as well.
  • Holes in the GI (gastrointestinal) tract may rarely happen.
  • High triglyceride levels have happened with Sylvant. Tell your doctor if you have ever had high triglyceride levels.
  • Have blood work checked as you have been told by the doctor. Talk with the doctor.
  • Some patients have very bad side effects during the infusion. Tell your doctor if you have any bad effects during the infusion.
  • Watch for gout attacks.
  • Birth control pills and other hormone-based birth control may not work as well to prevent pregnancy. Use some other kind of birth control also like a condom when taking Sylvant.
  • Women must use birth control while taking Sylvant and for some time after the last dose. Ask your doctor how long to use birth control. If you get pregnant, call your doctor right away.
  • If you used Sylvant when you were pregnant, tell your baby’s doctor.
  • Tell your doctor if you are breast-feeding. You will need to talk about any risks to your baby.

How is Sylvant best taken?

Use Sylvant as ordered by your doctor. Read all information given to you. Follow all instructions closely.

  • It is given as an infusion into a vein over a period of time.
  • Other drugs may be given to help with infusion side effects.

What do I do if I miss a dose?

  • Call your doctor to find out what to do.

What are the side effects of Sylvant that I need to call my doctor about immediately?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Signs of infection like fever, chills, very bad sore throat, ear or sinus pain, cough, more sputum or change in color of sputum, pain with passing urine, mouth sores, or wound that will not heal.
  • Signs of kidney problems like unable to pass urine, change in how much urine is passed, blood in the urine, or a big weight gain.
  • Dizziness or passing out.
  • Very bad belly pain.
  • Upset stomach or throwing up.
  • Back pain.
  • Chest pain.
  • A heartbeat that does not feel normal.
  • Flushing.
  • Swelling.
  • Any unexplained bruising or bleeding.

What are some other side effects of Sylvant?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

  • Constipation.
  • Headache.
  • Throat pain.
  • Weight gain.
  • Signs of a common cold.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.

If overdose is suspected:

If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

How do I store and/or throw out Sylvant?

  • If you need to store Sylvant at home, talk with your doctor, nurse, or pharmacist about how to store it.




  • NDC 73090-420-01
  • Single-Dose Vial
    Discard Unused Portion
  • sylvant®
    For Injection
  • 100 mg
  • For Intravenous
    Infusion Only
  • Reconstitution: Reconstitute with
    5.2 mL Sterile Water for Injection, USP.
    Dilution: Must be further diluted with
    5% Dextrose Injection, USP.
  • EUSAPharma
  • Rx Only


  • NDC 73090-421-01
  • Single-Dose Vial
    Discard Unused Portion
  • sylvant®
    For Injection
  • 400 mg
  • For Intravenous Infusion Only
  • Reconstitution: Reconstitute with
    20 mL Sterile Water for
    Injection, USP.
    Dilution: Must be further diluted with
    5% Dextrose Injection, USP.
  • EUSAPharma
    Rx Only


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