Why is it important for renal patients to take calcium (Ca) tablets and aluminum (Al) hydroxide tablets?

From the Guidelines

Renal patients should take calcium tablets and aluminum hydroxide tablets to manage complications of kidney disease, but with caution due to potential risks associated with long-term aluminum intake, as evidenced by the K/DOQI clinical practice guidelines 1. The primary goal of these medications is to control serum phosphorus levels and maintain a balanced calcium-phosphorus product. Calcium supplements, such as calcium carbonate, help maintain normal calcium levels in the blood, which is crucial since damaged kidneys cannot properly activate vitamin D needed for calcium absorption. These supplements also bind to phosphate in the digestive tract, helping to control high phosphate levels (hyperphosphatemia) that commonly occur in kidney disease. Aluminum hydroxide tablets function primarily as phosphate binders, preventing the absorption of dietary phosphate. However, due to the potential for neurotoxicity and osteomalacia associated with aluminum-containing phosphate binders, their use should be reserved for patients with serum phosphorus greater than 7.0 mg/dL (2.26 mmol/L) and only for short-term therapy, as recommended by the K/DOQI guidelines 1. Key considerations for prescribing these medications include:

• Calcium carbonate might be prescribed at 500-1000mg with meals
• Aluminum hydroxide dosing varies based on phosphate levels
• These medications should be taken with meals to effectively bind dietary phosphate
• Regular blood tests to monitor calcium, phosphate, and parathyroid hormone levels are necessary to adjust dosages appropriately It is essential to weigh the benefits of phosphate control against the potential risks of aluminum accumulation and to consider alternative phosphate binders, such as sevelamer, which has been shown to be effective in controlling serum phosphorus levels without the risks associated with aluminum-containing binders 1.

From the FDA Drug Label

Calcium acetate capsules are a phosphate binder indicated to reduce serum phosphorus in patients with end stage renal disease (ESRD). Calcium acetate, when taken with meals, combines with dietary phosphate to form an insoluble calcium phosphate complex, which is excreted in the feces, resulting in decreased serum phosphorus concentration. Patients with ESRD retain phosphorus and can develop hyperphosphatemia. High serum phosphorus can precipitate serum calcium resulting in ectopic calcification Hyperphosphatemia also plays a role in the development of secondary hyperparathyroidism in patients with ESRD.

The importance of calcium (Ca) tablets and aluminum (Al) hydroxide tablets for renal patients is due to their role in managing hyperphosphatemia.

• Calcium acetate acts as a phosphate binder, reducing serum phosphorus levels in patients with end-stage renal disease (ESRD).
• Although the provided drug labels do not directly mention aluminum hydroxide, it is known that aluminum hydroxide can also bind to phosphate in the gut, reducing its absorption and helping to control hyperphosphatemia in renal patients. However, the provided labels do not discuss the combined use of calcium and aluminum tablets, and the specific benefits or risks of this combination are not addressed 2, 2, 2.

From the Research

Importance of Calcium and Aluminum Tablets for Renal Patients

• Renal patients often require calcium (Ca) tablets and aluminum (Al) hydroxide tablets to manage their condition effectively 3, 4.
• Calcium carbonate is used as a phosphate binder in patients with chronic renal failure, helping to control serum phosphate concentrations 3.
• Aluminum hydroxide is also used as a phosphate binder, and its combination with calcium carbonate can help prevent hypercalcaemia and hyperaluminaemia 3, 4.
• The use of calcium acetate or calcium carbonate as phosphate binders can help prevent secondary hyperparathyroidism in uremic patients, which is essential for maintaining bone health 4.

Phosphate Binding Capacity

• Different phosphate binders have varying phosphate-binding capacities, with calcium acetate and calcium carbonate being commonly used 5.
• The relative phosphate-binding coefficient (RPBC) is used to estimate the phosphate-binding capacity of different binders, with calcium carbonate set as the reference point 5.
• Aluminum-containing binders, such as aluminum hydroxide and aluminum carbonate, have a higher RPBC compared to calcium carbonate 5.

Management of Chronic Kidney Disease-Mineral and Bone Disorders (CKD-MBDs)

• CKD-MBDs are a spectrum of abnormalities involving skeletal hormones, minerals, and bone turnover and mineralization 6.
• The management of CKD-MBDs involves the use of calcium, phosphate binders, vitamin D, and other medications to control serum phosphate and calcium levels 6.
• The association between CKD-MBDs and osteoporosis is complex, and the use of antifracture treatments is not approved for patients with kidney-associated bone disease 7.
• However, agents that suppress parathyroid hormone and antiresorptive and osteoanabolic agents are being used off-label to treat CKD stages 3b-5 in high-risk patients 7.