What is Burosumab: Uses, Dosage, Side Effects and More

Burosumab is a specialized medication that helps treat rare bone diseases by blocking a protein that interferes with phosphate absorption in your body. It's given as an injection under the skin and works by allowing your bones to get the phosphate they need to stay strong and healthy.

This medication represents a significant breakthrough for people with certain inherited bone conditions. While it may sound complex, burosumab essentially helps your body use phosphate more effectively, which is crucial for proper bone development and maintenance.

What is Burosumab?

Burosumab is a monoclonal antibody that targets a specific protein called FGF23. This protein normally helps regulate phosphate levels in your blood, but in certain genetic conditions, too much FGF23 causes your kidneys to waste phosphate that your bones desperately need.

Think of burosumab as a targeted blocker that reduces the activity of this troublesome protein. By doing so, it allows your kidneys to hold onto more phosphate, which then becomes available for your bones to use for proper mineralization and growth.

The medication comes as a clear liquid that's injected under your skin, similar to how people with diabetes might inject insulin. It's manufactured using advanced biotechnology and requires special handling and storage.

What is Burosumab Used For?

Burosumab is primarily used to treat X-linked hypophosphatemia (XLH), a rare genetic condition that affects how your body handles phosphate. This condition causes soft, weak bones that can lead to bowing of the legs, short stature, and dental problems.

The medication is also approved for treating tumor-induced osteomalacia (TIO), another rare condition where tumors cause your body to waste phosphate. In both cases, burosumab helps restore the phosphate balance your bones need to stay healthy.

Your doctor will only prescribe burosumab if you have a confirmed diagnosis of one of these specific conditions. Blood tests and genetic testing help determine if you're a candidate for this specialized treatment.

How Does Burosumab Work?

Burosumab works by blocking FGF23, a hormone that tells your kidneys to get rid of phosphate through urine. When there's too much FGF23 activity, your body loses phosphate it should be keeping for bone health.

By reducing FGF23's effects, burosumab allows your kidneys to reabsorb more phosphate from your urine back into your bloodstream. This increased phosphate availability helps your bones mineralize properly and become stronger over time.

The medication is considered a targeted therapy because it specifically addresses the root cause of phosphate wasting rather than just treating symptoms. This makes it particularly effective for the genetic conditions it's designed to treat.

How Should I Take Burosumab?

Burosumab is given as an injection under the skin, typically in your thigh, upper arm, or abdomen. Most people receive injections every two weeks, though your doctor will determine the exact schedule based on your specific needs.

You'll likely receive your first few injections at a healthcare facility where medical staff can monitor you for any reactions. Many people can eventually learn to give themselves injections at home, though this requires proper training from your healthcare team.

The medication needs to be stored in the refrigerator and should be brought to room temperature before injection. Never shake the vial, as this can damage the medication. Your healthcare provider will show you the proper injection technique and rotation of injection sites.

You can take burosumab with or without food, since it's injected rather than taken by mouth. However, your doctor may recommend avoiding calcium and vitamin D supplements for a few hours around injection time to prevent complications.

How Long Should I Take Burosumab For?

Burosumab is typically a long-term treatment that you may need to continue indefinitely. Since it treats genetic conditions that don't go away, stopping the medication usually means your symptoms will return.

Your doctor will monitor your progress through regular blood tests and imaging studies to ensure the medication continues working effectively. Some people may see improvements in bone strength and pain within a few months, while others may take longer to notice changes.

The duration of treatment depends on how well you respond to the medication and whether you experience any significant side effects. Your healthcare team will work with you to find the right balance between benefits and any potential risks.

What Are the Side Effects of Burosumab?

Like all medications, burosumab can cause side effects, though many people tolerate it well. Understanding what to expect can help you feel more prepared and know when to contact your healthcare provider.

The most common side effects you might experience include injection site reactions like redness, swelling, or mild pain where the needle went in. These reactions are usually mild and go away on their own within a day or two.

Common Side Effects

Here are the side effects that occur most frequently with burosumab treatment:

• Injection site reactions (redness, swelling, bruising)
• Headache
• Tooth abscess or dental problems
• Muscle or joint pain
• Fatigue
• Nausea
• Dizziness

Most of these side effects are manageable and tend to improve as your body adjusts to the medication. Your healthcare team can provide strategies to minimize discomfort and help you cope with any ongoing symptoms.

Serious Side Effects

While less common, some serious side effects require immediate medical attention. These include severe allergic reactions, kidney problems, or signs of abnormally high phosphate levels.

Watch for symptoms like severe rash, difficulty breathing, swelling of your face or throat, or changes in urination patterns. Additionally, very high phosphate levels can cause calcium deposits in soft tissues, leading to complications.

Your doctor will monitor you closely through regular blood tests to catch any serious side effects early. Never hesitate to contact your healthcare provider if you experience anything unusual or concerning.

Who Should Not Take Burosumab?

Burosumab isn't suitable for everyone, and certain medical conditions or circumstances may make it unsafe for you. Your doctor will carefully evaluate your medical history before prescribing this medication.

You should not take burosumab if you have severe kidney disease, as this can increase your risk of dangerous complications. People with certain heart conditions or those taking specific medications may also need to avoid this treatment.

Pregnant and breastfeeding women should discuss the risks and benefits with their healthcare provider, as the effects of burosumab on developing babies aren't fully understood. Your doctor may recommend alternative treatments during these times.

Burosumab Brand Names

Burosumab is sold under the brand name Crysvita in the United States and many other countries. This is currently the only brand name available for this medication.

Since burosumab is a specialized biologic medication, there are no generic versions available. The medication is manufactured by Ultragenyx Pharmaceutical and requires special handling throughout the distribution process.

When receiving your medication, always verify that you're getting Crysvita and check the expiration date. If you notice any changes in the medication's appearance, such as discoloration or particles, don't use it and contact your pharmacy immediately.

Burosumab Alternatives

Currently, there are no direct alternatives to burosumab for treating X-linked hypophosphatemia and tumor-induced osteomalacia. However, traditional treatments are still available and may be appropriate for some people.

Conventional treatment typically involves taking oral phosphate supplements along with active vitamin D medications like calcitriol. While these treatments can help manage symptoms, they require frequent dosing and careful monitoring to avoid complications.

Your doctor might consider combination approaches, using burosumab alongside other supportive treatments. The choice depends on your specific condition, response to treatment, and individual health factors.

Is Burosumab Better Than Traditional Phosphate Supplements?

Burosumab offers several advantages over traditional phosphate supplements and vitamin D therapy. Most notably, it addresses the underlying cause of phosphate wasting rather than just trying to replace what's being lost.

Traditional treatments require taking multiple pills several times daily and can cause stomach upset, diarrhea, and other digestive problems. Burosumab, given as an injection every two weeks, often provides more consistent phosphate levels with fewer daily medication burdens.

However, traditional treatments have been used longer and may be more appropriate for some people. Your doctor will consider factors like your age, severity of symptoms, and personal preferences when determining the best treatment approach for you.