Hypophosphatemic Rickets Medication

Updated: May 02, 2018
  • Author: James CM Chan, MD; Chief Editor: Sasigarn A Bowden, MD  more...
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Medication

Medication Summary

Burosumab (Crysvita) is the first drug approved in the U.S. for X-linked hypophosphatemia (XLH). It is a monoclonal IgG1 antibody that binds excess fibroblast growth factor 23 (FGF23). This action normalizes phosphorus levels, improves bone mineralization, improves rickets in children, and helps to heal fractures in adults. [8, 9, 10]

Other treatment options include calcitriol, GH, phosphates, and anticalciurics to promote healthy bone growth and diminish mineral loss associated with hypophosphatemic rickets. As previously stated, acute hypercalcemia (with resulting irritability, confusion, and potential seizures) can occur during treatment. Nephrocalcinosis, the long-term result of overaggressive therapy, [11] may be more damaging.

Unless a concomitant GH deficiency is observed, administration of biosynthetic GH for growth promotion has not been approved. Only preliminary evidence of improved final height with GH therapy has been reported. [31]

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Monoclonal Antibodies, Endocrine

Class Summary

The first targeted therapy directed toward correcting renal phosphate wasting, an underlying etiology of X-linked hypophosphatemia (XLH), has been approved in the United States.

Burosumab (Burosumab-twza, Crysvita)

Recombinant fully human monoclonal IgG1 antibody that binds fibroblast growth factor 23 (FGF23). This binding inhibits the biological activity of FGF23, thereby restoring renal phosphate reabsorption and increasing the serum concentration of 1,25 dihydroxy vitamin D. Burosumab is indicated for XLH in adults and children aged 1 year or older.

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Vitamin D

Class Summary

Standard protocol for treatment of familial hypophosphatemic rickets includes the use of 1,25-dihydroxy-vitamin D (calcitriol). The use of calcitriol in place of standard vitamin D obviates near-toxic dosage of the latter, avoids fat storage of parent vitamin D, and diminishes the danger of hypercalcemia.

Calcitriol (Rocaltrol)

Calcitriol increases calcium levels by promoting calcium absorption in the intestines and retention in kidneys.

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Phosphate replacement

Class Summary

Massive urinary phosphate loss is a problem intrinsic to the disorder, and the phosphate must be replaced.

Potassium phosphate/sodium acid phosphate (K-Phos Neutral, Phos-Nak)

This is a neutralized, buffered, oral phosphate-replacement solution containing 250 mg phosphorus, 280 mg potassium, 160 mg sodium . It is a combination of sodium and potassium phosphate.

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Diuretics

Class Summary

Thiazides are anticalciuric, an effect that can assist in counteracting the tendency for bone calcium loss.

Hydrochlorothiazide (Microzide)

Hydrochlorothiazide is a well-known diuretic with antihypertensive action. It inhibits reabsorption of sodium in distal tubules, causing increased excretion of sodium and water, as well as of potassium and hydrogen ions. Hydrochlorothiazide is not metabolized and is rapidly excreted in the urine.

Amiloride

Hypokalemia is a hazard when kaliuretic-effect thiazides are used; this danger that can be counteracted with the use of a second diuretic. Amiloride has a well-characterized antikaliuretic effect. Often used together with thiazides for its synergistic antihypertensive effects, amiloride has the benefit of decreasing potassium loss. Thus, it is a useful adjunct in the treatment of patients with familial X-linked hypophosphatemia with thiazides, in whom hypokalemia is a risk.

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