What are the treatment options for hyperphosphatemia?

Treatment Options for Hyperphosphatemia

The treatment of hyperphosphatemia should focus on phosphate-lowering therapies only in cases of progressive or persistent hyperphosphatemia, not for prevention, and should include dietary phosphate restriction, phosphate binders, and addressing underlying causes. 1

Dietary Phosphate Restriction

• Limiting dietary phosphate intake is recommended as a first-line approach for treating hyperphosphatemia, either alone or in combination with other treatments 1
• Consider phosphate source when making dietary recommendations, as bioavailability differs between food types:
  • Animal-based phosphate is absorbed at 40-60% 1
  • Plant-based phosphate (associated with phytates) is less absorbable (20-50%) 1
  • Inorganic phosphate in food additives has higher absorption 1, 2
• Guide patients toward fresh and homemade foods rather than processed foods to avoid hidden phosphate additives 1, 2
• For dialysis patients, phosphorus intake should be limited to approximately 750 mg/day, which corresponds to a protein diet of 45-50 g/day or 0.8 g/kg body weight/day for a 60 kg patient 3

Phosphate Binders

When to Initiate Phosphate Binders

• Phosphate-lowering therapies should only be initiated in cases of progressive or persistent hyperphosphatemia, not for prevention 1
• Normophosphatemia is not an indication to start phosphate-lowering treatments 1

Types of Phosphate Binders

1. Calcium-based phosphate binders

   • Calcium acetate or calcium carbonate are effective but should be used with caution 1
   • Restrict the dose of calcium-based phosphate binders to avoid excess calcium exposure, which may be harmful across all GFR categories of CKD 1, 4
   • The average daily dose of calcium acetate or carbonate used in clinical trials ranges between 1.2 and 2.3 g of elemental calcium 4
   • Modest doses (<1 g of elemental calcium) may represent a reasonable initial approach 4

2. Non-calcium-based phosphate binders

   • Consider when calcium-based binders are contraindicated or when large doses of binders are required 4
   • Options include:
     • Sevelamer: No potential for systemic accumulation and may have beneficial effects on cardiovascular disease 4, 5
     • Lanthanum carbonate: Effective but has biliary excretion 4, 5
     • Magnesium salts: Effective but have urinary excretion 4
     • Iron-based binders: Have powerful phosphate-binding capability 5

3. Aluminum-containing binders

   • Efficient but no longer widely used due to toxicity concerns 4

Dialysis Management

• For patients on dialysis, ensure efficient dialysis removal of phosphate 4
• Conventional hemodialysis with a high-flux, high-efficiency dialyzer removes approximately 30 mmol (900 mg) phosphorus during each dialysis performed three times weekly 3

Integrated Approach and Monitoring

• Target levels should aim for:

  • Phosphorus: 2.5-5.5 mg/dl 3
  • Calcium-phosphorus product: <55 mg²/dl² 3
  • PTH: 100-200 pg/ml for intact parathyroid hormone 3

• Monitor for development of hypercalcemia when using calcium-based binders 6

• If hyperphosphatemia persists despite dietary restrictions and phosphate binders, evaluate for:

  • Medication adherence issues 7
  • Adequate dialysis (if applicable) 7
  • Hidden dietary phosphate sources 1, 2

Special Considerations

• In predialysis patients, if serum phosphorus exceeds 5.0-5.5 mg/dL, calcium-containing phosphate-binding agents (calcium carbonate or calcium acetate) should be taken with meals 8
• For patients with hyperphosphatemia and elevated PTH, addressing modifiable factors including vitamin D deficiency may be beneficial 1
• If hyperphosphatemia develops during treatment of hypocalcemia, consider phosphate binders 9

Potential Pitfalls and Caveats

• Excess exposure to calcium from calcium-based binders may be harmful across all GFR categories of CKD 1
• Aluminum-containing phosphate binders should be used with caution due to risk of aluminum accumulation 8, 4
• Dietary phosphate restriction alone is usually not sufficient to control serum phosphate levels in most CKD patients 4
• Low-income populations are particularly at risk for dietary phosphate overload due to higher amounts of phosphate in inexpensive, processed foods 2
• Calcium acetate, when taken in excess, may result in hypercalcemia 6