What are the recommendations for using phosphate binders, such as sevelamer (phosphorus binder) or lanthanum carbonate (phosphate binder), in the management of hyperphosphatemia in tumor lysis syndrome?

Phosphate Binders in Tumor Lysis Syndrome Management

For hyperphosphatemia in tumor lysis syndrome (TLS), aluminum hydroxide (50-100 mg/kg/day) is recommended as first-line treatment for mild hyperphosphatemia, while sevelamer is an effective alternative especially when aluminum toxicity is a concern or in cases requiring longer treatment. 1

Initial Management of Hyperphosphatemia in TLS

Mild Hyperphosphatemia (<1.62 mmol/L)

• First eliminate phosphate from intravenous solutions and maintain adequate hydration 1
• Administer phosphate binders:
  • Aluminum hydroxide: 50-150 mg/kg/day divided in 4 doses (orally or via nasogastric tube) 1
  • Limit aluminum hydroxide use to 1-2 days to avoid cumulative aluminum toxicity 1

Alternative Phosphate Binders

• Sevelamer hydrochloride:
  • Pediatric dosing: 400 mg twice to thrice daily (based on weight) 2, 3
  • Adult dosing: Start with 800-1600 mg three times daily with meals, titrate based on phosphate levels 4
  • Advantages: No aluminum toxicity risk, effective in TLS-associated hyperphosphatemia 2, 3, 5
• Lanthanum carbonate: Alternative non-calcium, non-aluminum phosphate binder 1
• Calcium carbonate: Only use if calcium levels are low; contraindicated in hypercalcemia 1, 6

Monitoring and Dose Adjustment

• Monitor serum phosphate levels:
  • Every 24 hours during initial treatment 2, 5
  • Titrate dose based on phosphate levels 4
• Monitor calcium-phosphate product 2, 3
• For sevelamer: Increase or decrease by one tablet per meal at two-week intervals as necessary 4

Evidence for Sevelamer in TLS

Recent studies demonstrate sevelamer's efficacy in TLS-associated hyperphosphatemia:

• Mean phosphate levels decreased from 8.3 ± 3.0 to 6.7 ± 2.1 mg/dl within 24 hours of starting sevelamer 2
• Continued reduction to 4.39 ± 1.7 mg/dl at 96 hours 2
• TLS corrected within 72 hours in most patients 2, 5
• Calcium-phosphate product decreased from 63.0 ± 14.0 to 39.7 ± 13.5 mg/dl within 72 hours 2
• Minimal side effects reported (mild vomiting in some patients) 3

Severe Hyperphosphatemia Management

For severe hyperphosphatemia unresponsive to phosphate binders:

• Hemodialysis is most effective for phosphate clearance 1
• Alternatives: peritoneal dialysis or continuous venovenous hemofiltration 1
• Early start of renal replacement therapy is advised to remove phosphate and improve associated electrolyte abnormalities 1

Important Considerations and Caveats

• Calcium-containing phosphate binders should be avoided in patients with hypercalcemia 1, 6
• Sevelamer may cause metabolic acidosis and can reduce bioavailability of certain medications (ciprofloxacin, mycophenolate mofetil, levothyroxine) 4
• Aluminum hydroxide should be limited to short-term use (1-2 days) due to risk of aluminum toxicity 1
• Pediatric patients might find aluminum hydroxide taste objectionable, making sevelamer a practical alternative 1
• Phosphate clearance is better with hemodialysis compared to continuous venovenous hemofiltration or peritoneal dialysis when needed 1

By following these guidelines for phosphate binder use in TLS, hyperphosphatemia can be effectively managed while minimizing complications and improving patient outcomes.