Crysvita (burosumab) is a human monoclonal antibody that is used to treat X-linked hypophosphatemia (XLH) in adults and children aged 1 year and older. XLH is a rare genetic disorder that causes low levels of phosphate in the blood. Phosphate is a mineral that is essential for bone health. People with XLH are at risk of developing bone deformities, fractures, and other complications.

Description

Crysvita is a clear, colorless solution that is administered by subcutaneous injection (an injection just under the skin). It is available in single-dose prefilled syringes in two strengths: 10 mg/mL and 20 mg/mL.

Uses

Crysvita is used to treat XLH, a rare genetic disorder that causes low levels of phosphate in the blood. Phosphate is a mineral that is essential for bone health. People with XLH are at risk of developing bone deformities, fractures, and other complications.

How to Use

Crysvita is given by subcutaneous injection once a week. Your doctor or nurse will show you how to inject Crysvita at home. If you are using the prefilled syringe, you will need to prime the syringe before your first injection.

Dosage

The recommended dosage of Crysvita is based on weight and is adjusted based on individual response. The starting dosage is 0.8 mg/kg for adults and 0.4 mg/kg for children. The dosage may be increased by 0.2 mg/kg every 4 weeks until the desired phosphate level is reached.

Mechanism of Action

Crysvita works by blocking the activity of fibroblast growth factor 23 (FGF23), a hormone that lowers phosphate levels in the blood. By blocking FGF23, Crysvita can help to increase phosphate levels and improve bone health.

Storage Conditions

Crysvita should be stored in the refrigerator at 36ºF to 46ºF (2°C to 8°C). It can be left at room temperature for up to 30 minutes before injecting.

Precautions

Crysvita should be used with caution in patients with a history of allergic reactions to other monoclonal antibodies. It is also important to tell your doctor about any other medications you are taking, including over-the-counter medications, herbal supplements, and vitamins.

Interactions

Crysvita may interact with other medications that affect the kidneys or the levels of phosphate or calcium in the blood. It is important to tell your doctor about all of the medications you are taking before starting Crysvita.

Contraindications

Crysvita is contraindicated in patients with a known hypersensitivity to burosumab or any of the excipients in the drug. Crysvita is also contraindicated in patients with hyperphosphatemia (high levels of phosphate in the blood).

Side Effects

The most common side effects of Crysvita are mild and transient. The most common side effects include:

• Injection site reactions (e.g., pain, redness, swelling)
• Headache
• Nausea
• Diarrhea
• Fatigue

Serious side effects of Crysvita are rare. However, serious side effects can occur, including:

• Allergic reactions
• Hypocalcemia (low levels of calcium in the blood)
• Hyperphosphatemia (high levels of phosphate in the blood)

If you experience any serious side effects while using Crysvita, stop using the medication and contact your doctor immediately.

Overdose

There is no information available on overdose of Crysvita. However, if you accidentally inject more Crysvita than prescribed, contact your doctor or poison control center immediately.

Additional Information

Crysvita is a relatively new drug, and it is still being studied. However, it has been shown to be effective in treating XLH in clinical trials. Crysvita is generally well-tolerated, and the most common side effects are mild and transient.