Treatment for Hyperphosphatemia
The treatment of hyperphosphatemia should begin with dietary phosphate restriction (800-1,000 mg/day) and, if ineffective, progress to phosphate binders, with non-calcium-based binders preferred in patients with vascular calcifications or hypercalcemia. 1
Assessment and Target Levels
Target Phosphate Levels
- CKD Stages 3-4: Maintain phosphate between 2.7-4.6 mg/dL 1
- CKD Stage 5/Dialysis: Maintain phosphate between 3.5-5.5 mg/dL 1
Monitoring Frequency
- CKD G3a-G3b: Every 6-12 months
- CKD G4: Every 3-6 months
- CKD G5/G5D: Every 1-3 months 2
Treatment Algorithm
Step 1: Dietary Phosphate Restriction
- Restrict dietary phosphate to 800-1,000 mg/day when:
- Serum phosphorus >4.6 mg/dL in CKD stages 3-4
- Serum phosphorus >5.5 mg/dL in CKD stage 5 1
- Consider phosphate sources:
- Animal-based phosphate: 40-60% absorption
- Plant-based phosphate: 20-50% absorption
- Inorganic phosphate (food additives): Highest bioavailability 2
- Monitor serum phosphate monthly after initiating dietary restrictions 1
Step 2: Phosphate Binders
If phosphate or PTH levels cannot be controlled with dietary restriction alone, initiate phosphate binders 1:
For CKD Stages 3-4:
- Calcium-based phosphate binders are effective and may be used as initial therapy 1
For CKD Stage 5/Dialysis:
- Both calcium-based and non-calcium-based binders are effective
- Selection criteria:
- For patients with hypercalcemia (>10.2 mg/dL): Use non-calcium binders 1
- For patients with PTH <150 pg/mL: Avoid calcium-based binders 1
- For patients with severe vascular/soft tissue calcifications: Prefer non-calcium binders 1
- For phosphorus >7.0 mg/dL: Consider short-term (4 weeks) aluminum-based binders as a last resort 1
Dosing Guidelines:
- Calcium acetate: Initial dose of 2 tablets (667 mg each) per meal, adjust as needed
Step 3: Combination Therapy
- For dialysis patients who remain hyperphosphatemic (>5.5 mg/dL) despite single-agent therapy, use a combination of calcium-based and non-calcium-based binders 1
Step 4: Intensify Dialysis (for dialysis patients)
- For persistent hyperphosphatemia >7.0 mg/dL, consider more frequent dialysis 1
Specific Phosphate Binders
Calcium-Based Binders
- Calcium acetate or calcium carbonate
- Advantages: Inexpensive, effective
- Disadvantages: Risk of hypercalcemia, vascular calcification, adynamic bone disease 4
- Clinical evidence: 30% decrease in serum phosphorus over 12 weeks with calcium acetate 3
Non-Calcium-Based Binders
- Sevelamer: No systemic accumulation, may reduce vascular calcification
- Lanthanum carbonate: Effective but has biliary excretion
- Iron-based binders: Effective phosphate binding capacity 5, 6
Common Pitfalls and Caveats
Avoid initiating phosphate-lowering therapy in normophosphatemic patients with CKD, as studies show potential harm without benefit 1
Monitor for hypercalcemia when using calcium-based binders, especially in dialysis patients 1
Recognize "hidden" phosphate sources in processed foods and additives, which have higher bioavailability than natural phosphate sources 2
Consider phosphate binder adherence issues - high pill burden can lead to poor compliance 6
Be aware that conventional hemodialysis only removes approximately 900 mg phosphorus per session, which is insufficient to maintain balance with typical dietary intake 7
Address secondary hyperparathyroidism by evaluating modifiable factors including hyperphosphatemia, hypocalcemia, high phosphate intake, and vitamin D deficiency 1
By following this structured approach to hyperphosphatemia management, focusing first on dietary modifications and then appropriate selection of phosphate binders based on patient characteristics, serum phosphate levels can be effectively controlled in most patients with CKD.