Hyperphosphatemia

Hyperphosphatemia, or elevated serum phosphorus, is a common disorder in CKD patients and is tightly linked to the progression of SHPT, bone disease, soft tissue mineralization and the progression of kidney failure.

The kidneys provide the primary route of excretion for excess phosphorus absorbed from ingested food. As kidney function worsens, elevation in blood levels of serum phosphorus directly stimulate PTH secretion by the parathyroid glands and exacerbate SHPT.

Since failing kidneys can no longer adequately handle the burden of excess phosphorus, CKD patients must control their diet to reduce phosphate intake.  Stage 5 CKD patients usually require treatment with phosphate-binding agents in an attempt to lower serum phosphorus to acceptable levels.

Serum levels of phosphorus are regularly monitored and controlled in CKD patients.  According to K/DOQI guidelines, serum phosphorus levels should be maintained at <5.5 mg/dL in patients with Stage 5 CKD.  In the U.S., approximately 90% of dialysis patients are treated with a phosphate control product.

In 2007, the FDA Advisory Committee on Cardiovascular and Renal Drugs recommended that the FDA extend the indications for existing phosphate binders to Stage 3 and 4 patients with hyperphosphatemia. While this recommendation acknowledged the need to control hyperphosphatemia in earlier stages of CKD, all currently approved phosphate binding agents have undesirable side effects that greatly affect patient compliance and, therefore, may be even less suitable for Stage 3 and 4 patients.

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