Mechanism of effect
Burosumab is a recombinant human monoclonal antibody (IgG1) that both binds to and inhibits the actions of fibroblast growth factor 23 (FGF23). By inhibiting this growth factor, burosumab increases the tubular reabsorption of phosphate from the kidney and thus increases serum concentration of 1, 25 dihydroxy-Vitamin D. This form of vitamin D enhances intestinal absorption of phosphate and calcium, supporting bone mineralization.
Pharmacodynamic
This drug has the ability to reduce the loss of phosphate, to improve pathologically low serum phosphate concentrations and other metabolic changes, as well as to reduce the severity of rickets as seen radiographically. In summary, this drug works to support of bone mineralization.
Pharmacokinetics
Steady-state trough: 5.8 mcg/mL
Peak plasma time: 8-11 days
Vd: 8 L
Metabolism: Exact metabolic pathway has not been characterized; expected to degrade into small peptides and amino acids via catabolic pathways
Half-life: ~19 days
Clearance is 0.290 L/day
Dosage
X-Linked Hypophosphatemia
Adult
Indicated for X-linked hypophosphatemia (XLH), a rare inherited form of rickets
1 mg/kg SC q4Weeks; round dose to nearest 10 mg
Not to exceed 90 mg/dose
Pediatric
<1 year: Safety and efficacy not established
≥1 year: 0.8 mg/kg SC q2Weeks; round dose to nearest 10 mg
Minimum weight-based starting dose is 10 mg up to a maximum dose of 90 mg
Side effects
Headache , vomiting , vertigo , urticaria , fever , myalgia , Injection-site reaction , Rash , HypersensitivityInteractions
Dihydrotachysterol , Cinacalcet , Calcitriol , sodium phosphates , Potassium Phosphate , Paricalcitol , Doxercalciferol , Calcifediol , alirocumabAlerts
Hypersensitivity reactions (eg, rash, urticaria) reported; discontinue if serious hypersensitivity reactions occur and initiate appropriate medical treatment
Increases in serum phosphorus to >ULN may be associated with increased risk of nephrocalcinosis; for patients already taking burosumab, dose interruption and/or dose reduction may be required based serum phosphorus levels
Local injection site reactions may occur; discontinue if severe injection site reactions occur and administer appropriate medical treatment
Points of recommendation
At least 1 week before your first injection, stop using oral phosphate and vitamin D medications.
Burosumab doses are based on weight in children. Your child's dose needs may change if the child gains or loses weight.
You may need frequent medical tests. Even if you have no symptoms, tests can help your doctor determine if this medicine is effective.
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