Mepolizumab is a monoclonal antibody that works by reducing levels of eosinophils (a type of white blood cell). High eosinophil levels can contribute to certain disorders.

Mepolizumab is used to help prevent flare-ups or reduce symptoms of high eosinophil levels (hypereosinophilic syndrome, or HES) in adults and children at least 12 years old.

Mepolizumab is also used in adults to help control symptoms and reduce flares of a rare autoimmune disorder called eosinophilic granulomatosis with polyangiitis (EPGA).

Mepolizumab is also used together with other medicines to help control severe asthma in adults and children who are at least 6 years old. Mepolizumab is not a rescue medicine for asthma attacks.

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

Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Your doctor may perform blood tests to make sure you do not have conditions that would prevent you from safely using mepolizumab.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Mepolizumab is not a rescue medicine for asthma attacks. Use only fast-acting inhalation medicine for an attack. Seek medical attention if your breathing problems get worse quickly, or if you think your asthma medications are not working as well.

Mepolizumab is injected under the skin, usually once every 4 weeks. A healthcare provider may teach you how to properly use the medication by yourself. Follow all directions on your prescription label

Mepolizumab powder must be mixed with a liquid (diluent) before using it. Read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you don't understand all instructions.

Gently swirl but do not shake the mixed medicine. Prepare an injection only when you are ready to give it. Do not use if the medicine has changed colors or has particles in it. Call your pharmacist for new medicine.

Store the vial (bottle) in its original carton at room temperature. Protect from light and do not freeze.

Store the prefilled syringe or autoinjector in the original carton in a refrigerator. Do not freeze or shake the medicine. After removing the medicine from the carton, you must use the syringe or autoinjector within 8 hours.

You may store the prefilled syringe or autoinjector in the unopened carton at room temperature for up to 7 days. Throw away a syringe or autoinjector left out of the refrigerator for more than 7 days.

Each vial, prefilled syringe, or autoinjector is for one use only. Throw it away after one use, even if there is still medicine left inside.

Use a needle and syringe only once and then place them in a puncture-proof "sharps" container. Follow state or local laws about how to dispose of this container. Keep it out of the reach of children and pets.

You should not use mepolizumab if you are allergic to it.

Mepolizumab is not approved for use by a child younger than 6 years old. Mepolizumab should not be used to treat HES in anyone younger than 12 years old, or EPGA in anyone younger than 18 years old.

Tell your doctor if:

• you also use steroid asthma medication;

• you have a history of parasite infection (such as roundworms or tapeworms); or

• you have a history of herpes zoster (also called shingles).

You may be given a zoster (shingles) vaccine before you start using mepolizumab.

If you also use an oral or inhaled steroid medication, you should not stop using it suddenly. Follow your doctor's instructions about tapering your dose.

Tell your doctor if you are pregnant. Your name may be listed on a pregnancy registry to track the effects of mepolizumab on the baby.

It may not be safe to breastfeed while using mepolizumab. Ask your doctor about any risk.

Use the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not use two doses at one time.

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, rash; wheezing, chest tightness, difficult breathing; feeling like you might pass out; swelling of your face, lips, tongue, or throat.

Mepolizumab may cause serious side effects. Call your doctor at once if you have:

• unusual pain or tiredness;

• burning or tingling anywhere in your body; or

• a red or blistering skin rash.

Common side effects of mepolizumab may include:

• headache;

• feeling tired;

• back pain; or

• pain, swelling, redness, burning, or itching where the medicine was injected.

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 mepolizumab, 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.