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Generic Name: siltuximab (sil TUX i mab)
Brand Names: Sylvant
Sylvant (siltuximab) is used to treat multicentric Castleman’s disease. Includes Sylvant side effects, interactions and dosage information.
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Drug Information:
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). Sylvant is used to treat Multicentric Castleman's Disease (MCD). MCD is a rare condition in which the body produces too much of a certain type of white blood cell. MCD can increase your risk of certain cancers by changing the way your immune system works. Sylvant is not for use in people who have human immunodeficiency virus (HIV) or human herpesvirus-8. Learn more

Sylvant Side Effects

Sylvant Side Effects

Note: This document contains side effect information about siltuximab. Some of the dosage forms listed on this page may not apply to the brand name Sylvant.

For the Consumer

Applies to siltuximab: intravenous powder for solution

Along with its needed effects, siltuximab (the active ingredient contained in Sylvant) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking siltuximab:

More common

  • Black, tarry stools
  • bleeding gums
  • bloating or swelling of the face, arms, hands, lower legs, or feet
  • bloody urine
  • blurred vision
  • body aches or pain
  • chills
  • confusion
  • cough
  • decreased frequency or amount of urine
  • difficulty with breathing
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • ear congestion
  • fever
  • full or bloated feeling
  • headache
  • increased thirst
  • loss of appetite
  • loss of voice
  • lower back or side pain
  • nasal congestion
  • nausea
  • pinpoint red spots on the skin
  • pressure in the stomach
  • rapid weight gain
  • runny nose
  • sneezing
  • sore throat
  • stomach pain
  • sweating
  • swelling of the abdominal or stomach area
  • tingling of the hands or feet
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • unusual weight gain or loss
  • vomiting

Less common

  • Back pain
  • chest pain or discomfort
  • dizziness
  • dry mouth
  • fainting
  • fast, irregular, pounding, or racing heartbeat or pulse
  • feeling of warmth
  • flushing or redness of the skin
  • lightheadedness
  • rapid breathing
  • redness of the face, neck, arms, and occasionally, upper chest
  • sunken eyes
  • unusually warm skin
  • wrinkled skin


  • Difficulty with swallowing
  • hives, itching, or skin rash
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • tightness in the chest

Some side effects of siltuximab may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  • Difficulty having a bowel movement
  • difficulty with moving
  • joint pain, stiffness, or swelling
  • muscle pain or stiffness
  • rash with flat lesions or small raised lesions on the skin

Less common

  • Darkening of the skin
  • decreased appetite
  • dry skin
  • skin rash, encrusted, scaly, and oozing

For Healthcare Professionals

Applies to siltuximab: intravenous powder for injection


The most common adverse reactions were pruritus, weight gain, rash, hyperuricemia, and upper respiratory tract infection.


Very common (10% or more): Upper respiratory tract infection (63%), nasopharyngitis (13%)

Common (1% to 10%): Lower respiratory tract infection, oropharyngeal pain


Very common (10% or more): Rash (28%), pruritus (28%), eczema

Common (1% to 10%): Skin hyperpigmentation, psoriasis, dry skin


Very common (10% or more): Diarrhea (32%), abdominal pain/abdominal distention (12%), oropharyngeal pain, nausea, vomiting, constipation, gastroesophageal reflux disease, mouth ulceration

Frequency not reported: Gastrointestinal perforation


Very common (10% or more): Weight gain (19%), hyperuricemia (11%), localized edema

Common (1% to 10%): Hypertriglyceridemia, hypercholesterolemia, decreased appetite, dehydration


Very common (10% or more): Edema (26%), hypertension

Common (1% to 10%): Hypotension


Common (1% to 10%): Anaphylactic reaction


Very common (10% or more): Fatigue (21%)


Very common (10% or more): Pain in extremities (21%), arthralgia (21%)


Common (1% to 10%): Renal impairment


Very common (10% or more): Thrombocytopenia, neutropenia

Nervous system

Very common (10% or more): Headache, dizziness


Uncommon (0.1% to 1%): Positive test for anti-siltuximab (the active ingredient contained in Sylvant) antibodies


Common (1% to 10%): Infusion related reactions (e.g., back pain, chest pain/discomfort, nausea, vomiting, flushing, erythema, palpitations)


Very common (10% or more): Urinary tract infection

Editorial References and Review

Medically reviewed by BestRx Medical Team Last updated on 1/1/2020.

Source: Drugs.com Sylvant