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Generic Name: siltuximab (sil TUX i mab)
Brand Names: Sylvant

Medically reviewed by P. Thornton, DipPharm Last updated on Mar 4, 2019.

What is Sylvant?

Sylvant (siltuximab) inhibits a certain protein in the body called interleukin-6 (IL-6). High levels of IL-6 can cause an overgrowth of cells in the lymph system (part of your immune system).



Important information

You should not use Sylvant if you have a severe infection. Tell your doctor if you have recently had any signs of infection (fever, chills, body aches).

Before taking this medicine

You should not be treated with Sylvant if you are allergic to siltuximab, or if you have a severe infection.


To make sure Sylvant is safe for you, tell your doctor if you have ever had:

  • a chronic infection;

  • a stomach or intestinal disorder, including ulcer or diverticulitis;

  • stomach or intestinal bleeding;

  • gout; or


Sylvant may harm an unborn baby. Siltuximab an affect the immune system of a newborn if the mother receives the medicine during pregnancy. Uee effective birth control to prevent pregnancy while you are using this medicine and for at least 3 months after your last dose.

You should not breast-feed while using this medicine.

How is Sylvant given?

Sylvant is given as an infusion into a vein, usually once every 3 weeks. A healthcare provider will give you this injection. Follow your doctor's dosing instructions very carefully.

Before each injection, your doctor may perform blood tests to make sure you do not have conditions that would prevent you from safely using Sylvant.

Siltuximab can increase your risk of bleeding or infection. You will need frequent medical tests. Your treatments may be delayed based on the results.

Sylvant must be given slowly and the IV infusion can take at least 1 hour to complete.

Siltuximab can lower blood cells that help your body fight infections. Your blood will need to be tested often. Your treatments may be delayed based on the results of these tests.

Sylvant dosing information

Usual Adult Dose for Castleman's Disease:

11 mg/kg intravenously over 1 hour every 3 weeks.

Duration of therapy: Until treatment failure.

-Siltuximab was not studied in patients with MCD who are HIV positive or HHV-8 positive because siltuximab did not bind to virally produced IL-6 in a nonclinical study.


What happens if I miss a dose?

Call your doctor for instructions if you miss an appointment for your Sylvant injection.

What happens if I overdose?


What should I avoid while receiving Sylvant?

Do not receive a "live" vaccine while using Sylvant. The vaccine may not work as well and may not fully protect you from disease. Live vaccines include measles, mumps, rubella (MMR), polio, rotavirus, typhoid, yellow fever, varicella (chickenpox), zoster (shingles), and nasal flu (influenza) vaccine.

Sylvant side effects

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


Call your doctor at once if you have:


  • signs of a kidney problem - little or no urination; painful or difficult urination; swelling in your feet or ankles; severe pain in your side or lower back.

Common Sylvant side effects may include:

  • weight gain;

  • itching or rash;




What other drugs will affect Sylvant?


Further information

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