Siltuximab injection is used to treat multicentric Castleman’s disease (MCD; abnormal overgrowth of lymph cells in more than one part of the body that may cause symptoms and may increase the risk of developing a serious infection or cancer) in people who do not have human immunodeficiency virus (HIV) and human herpesvirus-8 (HHV-8) infection. Siltuximab is in a class of medications called monoclonal antibodies. It works by blocking the action of a natural substance that causes increased growth of lymph cells in people with MCD.

Siltuximab injection comes as a liquid to be injected intravenously (into a vein) over 1 hour by a healthcare provider in a hospital or medical office. It is usually given once every 3 weeks.

You may experience a reaction when you receive siltuximab injection. If you experience a reaction, your healthcare provider will stop your infusion and will give you medication to treat your reaction. If your reaction is severe, your healthcare provider may not give you any more infusions of siltuximab. Tell your healthcare provider or get emergency medical treatment if you experience any of the following symptoms during or after your infusion: trouble breathing; chest tightness; wheezing; dizziness or light-headedness; swelling of the face, lips, tongue or throat; rash; itching; headache; back pain; chest pain; nausea; vomiting; flushing; reddening of the skin; or pounding heartbeat.

Siltuximab injection may help to control MCD but does not cure it. Continue to keep appointments to receive siltuximab injection even if you feel well.

Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Before receiving siltuximab injection,

• Tell your doctor and pharmacist if you are allergic to siltuximab injection, any other medications, or any of the ingredients in siltuximab injection. Ask your pharmacist or check the manufacturer’s patient information for a list of the ingredients.
• Tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: anticoagulants (‘blood thinners’) such as warfarin (Coumadin, Jantoven), atorvastatin (Lipitor), cyclosporine (Gengraf, Neoral, Sandimmune), lovastatin (in Altoprev), oral contraceptives (birth control pills), and theophylline ( Theo-24, Uniphyl). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• Tell your doctor if you have any type of infection before you begin your treatment with siltuximab injection, or if you notice any signs of infection during your treatment. Also tell your doctor if you have or have ever had any condition that affects your stomach or intestines such as ulcers (sores in the lining of the stomach or intestines) or diverticulitis (small pouches in the lining of the intestine that may become inflamed).
• Tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. You should use birth control to prevent pregnancy during your treatment with siltuximab injection and for three months after your treatment. Talk to your doctor about methods of birth control that will work for you. If you become pregnant while receiving siltuximab injection, call your doctor immediately. Siltuximab may harm the fetus.
• Do not have any vaccinations without talking to your doctor. Also tell your doctor if you have recently received any vaccinations. Talk to your doctor about whether you should receive any vaccinations before you begin your treatment.

Unless your doctor tells you otherwise, continue your normal diet.

If you miss an appointment to receive a dose of siltuximab injection, call your doctor as soon as possible.

Siltuximab injection may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• Darkening of the skin
• Dry skin
• Constipation
• Mouth or throat pain
• Weight gain

Some side effects can be serious. If you experience any of these symptoms or those in the HOW section, call your doctor immediately or get emergency medical treatment:

• Fever, sore throat, chills, or other signs of infection
• Unusual bruising or bleeding
• Swelling of the hands, arms, feet, ankles, or lower legs

Siltuximab injection may cause other side effects. Call your doctor if you have any unusual problems while you are taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body’s response to siltuximab injection.

Ask your pharmacist any questions you have about siltuximab injection.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.