What are the various phosphate binders used to treat hyperphosphatemia in chronic kidney disease?

Phosphate Binders for Hyperphosphatemia in Chronic Kidney Disease

Available Phosphate Binder Classes

Multiple classes of phosphate binders are clinically available to treat hyperphosphatemia in CKD, including calcium-based binders, polymeric binders (sevelamer, bixalomer, colestilan), lanthanum carbonate, iron-based binders (ferric citrate, sucroferric oxyhydroxide), and magnesium-containing binders. 1, 2

Calcium-Based Phosphate Binders

• Calcium acetate and calcium carbonate are the traditional first-line agents that effectively lower serum phosphate levels 2, 3
• These binders are well-tolerated but carry significant risk of calcium overload, hypercalcemia, and progression of vascular calcification 1, 4
• The 2017 KDIGO guidelines specifically recommend restricting the dose of calcium-based phosphate binders due to safety concerns about excess calcium exposure across all CKD stages 5
• Studies demonstrate that calcium-based binders may cause positive calcium balance even in normophosphatemic patients with CKD G3b-G4, potentially accelerating vascular calcification 5

Polymeric Phosphate Binders

• Sevelamer (hydrochloride or carbonate) is a non-calcium, non-metal polymer that binds phosphate in the gastrointestinal tract 2, 3
• In CKD G5D patients on dialysis, sevelamer may lower all-cause mortality compared to calcium-based binders (RR 0.53,95% CI 0.30-0.91), reducing death risk from 210 per 1000 to 105 per 1000 over up to 36 months 6
• Sevelamer reduces serum cholesterol levels and exerts anti-inflammatory effects beyond phosphate binding 1
• The main adverse effect is constipation (RR 6.92,95% CI 2.24-21.4 compared to placebo) and other gastrointestinal symptoms 6, 4
• Bixalomer is associated with fewer gastrointestinal symptoms compared to sevelamer 1
• Colestilan is another polymeric option with similar mechanism of action 2, 3

Lanthanum Carbonate

• Lanthanum carbonate exhibits strong phosphate-lowering activity and is highly effective 1, 2
• It probably increases constipation compared to placebo (RR 2.98,95% CI 1.21-7.30) and may result in vomiting (RR 3.72,95% CI 1.36-10.18) 6
• Lanthanum is absorbed in the gut with tissue deposition, but long-term effects appear clinically irrelevant based on available data 4, 7
• Compared to calcium-based binders, lanthanum probably reduces treatment-related hypercalcemia (RR 0.16,95% CI 0.06-0.43) 6
• Lanthanum carbonate is more cost-effective than calcium-based binders in high-income countries as a second-line option, particularly in pre-dialysis patients (pooled INB $4860.2) 8

Iron-Based Phosphate Binders

• Ferric citrate, sucroferric oxyhydroxide, and stabilized polynuclear iron(III)-oxyhydroxide have powerful phosphate-binding capability 2, 4, 3
• These binders exhibit strong phosphate-lowering activity comparable to lanthanum 1
• Ferric citrate reduces requirements for erythropoiesis-stimulating agents and intravenous iron doses 1
• Iron-based binders probably increase constipation (RR 2.66,95% CI 1.15-6.12) and probably result in diarrhea (RR 2.81,95% CI 1.18-6.68) 6
• Critical monitoring of iron metabolic markers is required to avoid iron overload 1
• No head-to-head studies compare iron-based binders to calcium-based binders 6

Magnesium-Containing Binders

• Magnesium carbonate and calcium acetate/magnesium carbonate combination products are available options 2, 3
• Long-term safety data for the calcium acetate/magnesium combination product are lacking 4

Aluminum-Containing Binders

• Aluminum hydroxide has strong phosphate-binding capacity but carries potentially serious toxic risks including bone disease and neurological complications 4, 7
• These agents are generally avoided due to safety concerns 2, 3

Key Clinical Considerations

When to Initiate Phosphate Binders

• Phosphate-lowering therapies should only be initiated for progressive or persistent hyperphosphatemia, not for prevention of hyperphosphatemia or to maintain normophosphatemia 5
• The 2017 KDIGO guideline abandoned the previous recommendation to maintain phosphate in the normal range for CKD G3a-G4 patients 5
• Evidence is lacking to demonstrate efficacy and safety of phosphate binders in CKD G3a-G4 patients without hyperphosphatemia 5

Combination Therapy Strategy

• Combined use of multiple phosphate binders can offer advantages of each agent while minimizing individual drawbacks 1
• This approach should be tailored to individual patient conditions and comorbidities 1
• However, increased pill burden and nonadherence emerge as significant problems with combination therapy 1

Common Pitfalls

• Not all phosphate binders are interchangeable—each has distinct safety profiles and off-target actions 5, 1
• Aggressive dietary phosphate restriction is difficult and may compromise adequate protein intake 5
• The bioavailability of phosphorus varies: animal-based (40-60% absorbed), plant-based (20-50% absorbed), and inorganic food additives (highly absorbed) 5
• Patient education should focus on phosphate sources, particularly avoiding "hidden" phosphates in food additives 5, 9