Eculizumab is used in adults to treat myasthenia gravis or neuromyelitis optica spectrum disorder.

Eculizumab is also used to prevent the breakdown of red blood cells in adults with paroxysmal nocturnal hemoglobinuria.

Eculizumab is used in adults and children weighing at least 11 pounds (5 kilograms) to treat a blood disease called atypical hemolytic uremic syndrome.

Eculizumab is available only under a special program. You must be registered in the program and understand the risks and benefits of eculizumab.

Eculizumab may also be used for purposes not listed in this medication guide.

You may get infections more easily, even serious or fatal infections. Call your doctor right away if you have a headache and fever with nausea or vomiting, skin rash, body aches, flu symptoms, confusion, sensitivity to light, or stiffness in your neck or back.

Read the Patient Safety Card about meningococcal infection and learn what symptoms to watch for. Keep the card with you at all times while using eculizumab and for at least 3 months after your last dose.

You must be vaccinated against meningococcal infection at least 2 weeks before treatment with eculizumab.

Your doctor will perform tests to make sure eculizumab is the right treatment for you.

Eculizumab is injected into a vein by a healthcare provider. The infusion can take at least 35 minutes to complete in adults, or up to 4 hours in children.

Eculizumab is not given every day. Follow your doctor's dosing instructions very carefully. The dosing schedule may be different for a child or teenager than for an adult.

Doses are based on weight in children and teenagers. Your child's dose may change if the child gains or loses weight.

You should be watched closely for at least 1 hour after each infusion, to make sure you do not have a reaction.

You may get infections more easily, even serious or fatal infections. You will need frequent medical tests.

You will receive a card listing the symptoms of meningococcal infection. Read this information and learn what symptoms to watch for. Keep the card with you at all times while using eculizumab and for at least 3 months after your last dose.

Do not stop receiving eculizumab without first talking to your doctor. Interrupting your treatment could cause sudden and serious effects on your red blood cells.

Eculizumab can effect your body for up to 3 months. You may need medical tests for 8 to 12 weeks if you stop using this medicine. Make sure any doctor who treats you knows that you've used eculizumab.

You should not use eculizumab if:

• you have a meningococcal infection; or

• you have not been vaccinated against meningitis.

Tell your doctor if you have a fever or any type of infection.

Your doctor may recommend certain vaccines. You must be vaccinated against meningococcal infection at least 2 weeks before you start treatment with eculizumab. If you were vaccinated in the past, you may need a booster dose.

Follow your doctor's instructions about using eculizumab if you are pregnant. It is very important to control your blood disorder during pregnancy to avoid unwanted effects in you or the baby.

Ask a doctor if it is safe to breastfeed while using this medicine.

Call your doctor for instructions.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

Get emergency medical help if you have signs of an allergic reaction: hives; chest pain, difficult breathing; feeling like you might pass out; swelling of your face, lips, tongue, or throat. These symptoms may occur during the injection.

Seek emergency medical attention if you have symptoms of meningitis:

• fever and a headache or skin rash;

• headache with nausea and vomiting;

• body aches, flu symptoms;

• confusion, increased sensitivity to light; or

• stiffness in your neck or back.

During or after your treatment with eculizumab call your doctor at once if you have:

• fever;

• pain or burning when you urinate;

• dangerously high blood pressure-- dizziness, weakness, numbness, confusion, blurred vision, vomiting, chest pain, cough, shortness of breath, seizure;

• kidney problems--swelling, urinating less, feeling tired or short of breath;

• signs of a blood cell disorder--pale skin, unusual tiredness, feeling light-headed, cold hands and feet, easy bruising, unusual bleeding, confusion, chest pain, trouble breathing, seizure (convulsions); or

• signs of a blood clot--sudden numbness or weakness, problems with speech or balance, rapid breathing, coughing up blood, pain or swelling in your arms or legs.

Common side effects of eculizumab may include:

• headache, dizziness;

• flu symptoms (fever, tiredness, aches, cough, sore throat);

• runny or stuffy nose, sinus pain;

• painful urination;

• nausea, vomiting, diarrhea, stomach pain;

• swelling in your legs or feet;

• bruising;

• muscle or joint pain, back pain;

• a blood cell disorder; or

• high blood pressure.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Other drugs may affect eculizumab, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.