What is the management of hyperphosphatemia?

Management of Hyperphosphatemia

In patients with CKD stages 3a-5D and hyperphosphatemia, initiate treatment with dietary phosphate restriction (targeting 800-1000 mg/day) combined with non-calcium-based phosphate binders as first-line therapy, reserving calcium-based binders for limited use due to cardiovascular calcification risk. 1

When to Initiate Treatment

• Treatment should only be initiated for progressive or persistent hyperphosphatemia, not for prevention in normophosphatemic patients 1, 2
• Base treatment decisions on serial assessments of phosphate, calcium, and PTH levels considered together, not phosphate alone 1
• Target serum phosphate levels toward the normal range (2.5-4.5 mg/dL) in CKD G3a-G5D patients 1

Step 1: Dietary Phosphate Restriction

• Limit dietary phosphate intake to 800-1000 mg/day as the initial approach, adjusting for protein requirements 2
• Prioritize fresh foods over processed foods, as inorganic phosphate additives have near-complete absorption compared to organic phosphate 1, 3
• Animal-based phosphate is absorbed at 40-60%, while plant-based phosphate (phytates) is absorbed at only 20-50% 3, 2
• Involve an experienced dietitian, as dietary restriction alone is typically insufficient to control hyperphosphatemia in most CKD patients 1, 2

Step 2: Phosphate Binder Selection

First-Line: Non-Calcium-Based Binders

• Sevelamer is the preferred first-line phosphate binder due to evidence showing prevention of vascular calcification progression compared to calcium-based binders 3, 2, 4
• Start sevelamer at 800-1600 mg with each meal, titrating up to a maximum of 13 g/day based on phosphate response 3
• Lanthanum carbonate is an alternative non-calcium binder with similar efficacy, though long-term tissue deposition effects require monitoring 4

Second-Line: Calcium-Based Binders (Use With Caution)

• Restrict elemental calcium from binders to ≤1000 mg/day (preferably <1 gram daily) to minimize cardiovascular calcification risk 2, 5, 6
• Calcium acetate is more potent than calcium carbonate and requires lower calcium doses for equivalent phosphate binding 7, 8
• Take calcium-based binders with meals to maximize dietary phosphate binding 2, 5, 7
• Avoid calcium-based binders entirely in patients with: hypercalcemia, suppressed PTH (<150 pg/mL), severe vascular calcification, or adynamic bone disease 1, 2, 5

When Calcium-Based Binders Are Acceptable

• May use calcium acetate or carbonate as initial therapy if serum calcium is normal and no vascular calcification is present 2, 6
• If calcium-based binders require >1 gram elemental calcium daily to control phosphate, switch to or add a non-calcium binder rather than increasing calcium dose 5, 6

Aluminum-Based Binders (Short-Term Only)

• Reserve aluminum hydroxide for severe hyperphosphatemia (>7.0 mg/dL) refractory to other agents 2, 5
• Limit use to maximum 4 weeks as a single course only, then switch to other agents due to aluminum toxicity risk 1, 2
• Avoid long-term use and dialysate aluminum contamination to prevent aluminum intoxication 1

Step 3: Dialysis Optimization (For CKD G5D Patients)

• Increase dialytic phosphate removal if hyperphosphatemia persists despite dietary restriction and binders 1
• Hemodialysis provides superior phosphate clearance (70-100 mL/min) compared to peritoneal dialysis or continuous renal replacement therapy 3, 5
• Consider more frequent or longer dialysis sessions if phosphate remains >5.5 mg/dL despite maximum medical therapy 2
• Use dialysate calcium concentration between 1.25-1.50 mmol/L (2.5-3.0 mEq/L) 1

Critical Safety Considerations

• Avoid hypercalcemia in all CKD stages by monitoring serum calcium closely with any phosphate binder 1
• Total calcium intake (dietary plus binders) should not exceed 2000 mg/day 2
• Excess calcium exposure from binders increases cardiovascular calcification risk and mortality across all GFR categories 2, 5
• Monitor phosphate, calcium, and PTH levels serially: every 1-3 months for calcium/phosphate and every 3-6 months for PTH in CKD G5/G5D 1

Combination Therapy for Refractory Hyperphosphatemia

• If phosphate remains >5.5 mg/dL despite monotherapy, combine calcium-based and non-calcium-based binders rather than maximizing either agent alone 2
• Address modifiable factors including vitamin D deficiency and high phosphate intake 1, 2
• Ensure adequate dialysis prescription before escalating binder doses 2, 9

Common Pitfalls to Avoid

• Do not use calcium-based binders in hypercalcemic patients or those with arterial calcification, as this worsens cardiovascular outcomes 1, 2, 5
• Do not exceed 1500 mg/day elemental calcium from binders alone, as higher doses increase hypercalcemia and vascular calcification risk 2, 5
• Do not rely on dietary restriction alone—most CKD patients require phosphate binders for adequate control 1, 2
• Avoid inadvertent consumption of phosphate additives in processed foods, which have near-complete absorption 1, 3