What are the indications for phosphate binders in Acute Kidney Injury (AKI)?

From the Guidelines

Phosphate binders are indicated in acute kidney injury (AKI) when hyperphosphatemia (serum phosphate >4.5-5.0 mg/dL) develops and persists despite dietary phosphate restriction, as supported by the Kidney Disease: Improving Global Outcomes 2017 clinical practice guideline update 1.

Indications for Phosphate Binders in AKI

• Hyperphosphatemia that is severe (>7.0 mg/dL) or moderate with accompanying symptoms or hypocalcemia
• Persistence of hyperphosphatemia despite dietary phosphate restriction

Common Phosphate Binders

• Calcium-based agents: calcium carbonate 500-1500 mg with meals or calcium acetate 667-1334 mg with meals
• Non-calcium based options: sevelamer carbonate 800-1600 mg with meals, lanthanum carbonate 500-1000 mg with meals
• Aluminum hydroxide 300-600 mg with meals, limited to short-term use due to toxicity risk

Dosing and Monitoring

• Dosing should be adjusted based on serum phosphate levels, aiming to normalize phosphate while minimizing side effects
• Calcium-based binders should be used cautiously in patients with hypercalcemia or vascular calcifications
• Regular monitoring of serum phosphate, calcium, and parathyroid hormone levels is essential to guide therapy

Rationale for Phosphate Binder Use in AKI

• The kidneys normally excrete excess phosphate, but this function is impaired in AKI, leading to phosphate retention
• Phosphate retention can cause hypocalcemia, secondary hyperparathyroidism, and soft tissue calcification
• Phosphate binders work by binding dietary phosphate in the gut, preventing its absorption, and are necessary to mitigate these complications in AKI patients with hyperphosphatemia.

From the Research

Indications for Phosphate Binders in Acute Kidney Injury (AKI)

• Hyperphosphatemia is a common condition in patients with AKI, and phosphate binders are used to control serum phosphorus levels 2
• The use of phosphate binders in AKI is not as well established as in chronic kidney disease (CKD), but they may be indicated in patients with severe hyperphosphatemia 3
• Phosphate binders may be used in AKI patients undergoing continuous renal replacement therapy (CRRT) to control hyperphosphatemia and improve outcomes 4
• The choice of phosphate binder should be individualized, considering the clinical context, costs, and individual tolerability, as well as the concomitant effects on other parameters of mineral metabolism 2

Phosphate Binders Available

• Calcium-based salts are inexpensive and effective, but may be associated with hypercalcaemia, parathyroid gland suppression, and vascular calcification 2
• Non-calcium-based phosphate binders, such as sevelamer, lanthanum carbonate, and magnesium salts, are available and may be used in patients who cannot tolerate calcium-based binders 2, 5
• Sevelamer is a non-calcium-containing phosphate binder that does not have potential for systemic accumulation and may have pleiotropic effects that impact on cardiovascular disease 2

Considerations for Phosphate Binder Use in AKI

• Phosphate levels should be monitored closely in AKI patients, especially those undergoing CRRT, to avoid hypophosphatemia or hyperphosphatemia 6, 4
• The use of phosphate-containing solutions for RRT may be considered to prevent hypophosphatemia in critically ill patients with AKI 6
• Phosphate binders should be used with caution in pregnant patients, as erroneous treatment of pseudohyperphosphatemia may be detrimental 3