From the Guidelines
Renal patients should avoid taking calcium carbonate and aluminum-containing tablets to manage hyperphosphatemia due to the potential risks of hypercalcemia and aluminum toxicity, as suggested by the most recent evidence 1.
Mechanism of Action
These medications act as phosphate binders in the gastrointestinal tract, binding to dietary phosphate and preventing its absorption into the bloodstream. However, the use of calcium-based phosphate binders should be restricted in patients with hyperphosphatemia across the CKD spectrum, as new evidence suggests that hypercalcemia may be harmful in all GFR categories of CKD 1.
Risks and Concerns
The potential risks of aluminum toxicity, including bone disease and neurological effects with long-term use, are a concern with aluminum-based binders 1. Additionally, the use of calcium-based phosphate binders may worsen soft-tissue calcification.
Recommendations
The current recommendation is to treat patients with PTH values that are progressively increasing or persistently above the upper limit of normal, and to avoid routine use of calcitriol or vitamin D analogues due to the increased risk for hypercalcemia 1.
- Patients should be monitored regularly for serum calcium, phosphate, and aluminum levels to prevent complications.
- Non-calcium, non-aluminum binders may be a safer alternative for managing hyperphosphatemia in renal patients.
- Future research should address the gaps in knowledge regarding the treatment of CKD-MBD, including the comparison of calcium-containing and calcium-free phosphate binders 1.
From the Research
Reasons for Taking Calcium Carbonate and Aluminum Tablets
- Renal patients take calcium carbonate and aluminum tablets to manage hyperphosphatemia, a common condition in late stages of chronic kidney disease 2.
- Hyperphosphatemia is often associated with elevated parathormone levels, abnormal bone mineralization, extra-osseous calcification, and increased risk of cardiovascular events and death 2.
- Calcium-based binders, such as calcium carbonate, are effective in lowering serum phosphorus levels, but can lead to hypercalcemia and/or positive calcium balance and progression of cardiovascular calcification 2.
Effectiveness of Calcium Carbonate as a Phosphate Binder
- Studies have shown that calcium carbonate can be an effective phosphate binder in patients with chronic renal failure undergoing dialysis 3, 4.
- Calcium carbonate has been found to lower serum phosphorus levels and raise serum calcium levels in the majority of patients, making it a satisfactory substitute for traditional phosphate binders that contain aluminum 4.
- However, the use of calcium carbonate as a phosphate binder can also lead to hypercalcemia, and the possibility of long-term side effects such as metastatic calcification requires further investigation 4.
Comparison with Aluminum Hydroxide
- Aluminum hydroxide is a commonly used phosphate binder, but it can be associated with aluminum toxicity and osteomalacia 3, 4.
- Calcium carbonate has been found to be a safer alternative to aluminum hydroxide, with fewer side effects and no risk of aluminum toxicity 3, 4.
- However, the addition of small doses of aluminum hydroxide to calcium carbonate can cause a large rise in serum aluminum concentrations, indicating an enhanced rate of absorption or aberrant compartmentalization of aluminum 5.
Calcium and Phosphorus Balance
- A study found that oral calcium carbonate affects calcium but not phosphorus balance in stage 3-4 chronic kidney disease, producing positive calcium balance and modest reduction in urine phosphorus excretion 6.
- The positive calcium balance produced by calcium carbonate treatment cautions against its use as a phosphate binder in patients with stage 3 or 4 CKD, if these findings can be extrapolated to long-term therapy 6.