This medication is used to treat low phosphate levels caused by a certain rare genetic problem (X-linked hypophosphatemia) or by a tumor (tumor-induced osteomalacia). It helps by reducing a hormone in your blood (fibroblast growth factor 23) which increases phosphate levels in your body. Normal phosphate levels are important for the growth and strength of bones, teeth, and muscles. Burosumab belongs to a class of drugs known as monoclonal antibodies.

Read the Patient Information Leaflet if available from your pharmacist before you start using burosumab and each time you get an injection. If you have any questions, ask your doctor or pharmacist.

This medication is given by injection under the skin of the abdomen, buttock, thigh, or upper arm by a health care professional. It is given as directed by your doctor, usually once every 2 or 4 weeks. The dosage is based on your medical condition, weight, labs (such as phosphate levels), and response to treatment.

Your doctor will direct you to stop certain medications (such as man-made forms of vitamin D and medications taken by mouth for phosphate levels) 1 week before starting this medication. Consult your doctor or pharmacist for more details.

Use this medication regularly to get the most benefit from it. To help you remember, mark your calendar with a reminder.

Injection site redness, pain, itching, or swelling may occur. Nausea, constipation, cough, dizziness, vomiting, headache, muscle pain, or diarrhea may also occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• symptoms of high phosphate levels (such as muscle cramps or numbness around the mouth)
• symptoms of tooth infections (such as tooth pain, swelling)

This medication can worsen or cause a certain medical condition (restless legs syndrome-RLS). Tell your doctor right away if you have symptoms of restless legs syndrome such as an unusual urge to move your legs or an uncomfortable/unpleasant feeling in the legs usually at night.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before using burosumab, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• kidney disease
• high levels of phosphate in your blood

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

During pregnancy, burosumab should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is unknown if this medication passes into breast milk. Consult your doctor before breastfeeding.

See also How to Use section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug are:

• certain medications that increase phosphate levels (such as potassium phosphate, sodium phosphate)
• certain man-made active forms of vitamin D drugs (such as calcifediol, calcitriol, doxercalciferol, paricalcitol)

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Lab and/or medical tests (such as phosphate levels, vitamin D levels, kidney function) should be done before you start using this medication and while you are using it. Keep all medical and lab appointments. Consult your doctor for more details.

It is important to get each dose of this medication as scheduled. If you miss a dose, ask your doctor or pharmacist right away for a new dosing schedule.

Not applicable. This medication is given in a hospital or clinic setting and will not be stored at home.