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# Calcium Acetate
## Overview
Calcium acetate is a phosphate binder used to reduce serum phosphate levels in patients with hyperphosphatemia, often associated with chronic kidney disease (CKD). It works by binding to dietary phosphate in the gastrointestinal tract, forming an insoluble calcium phosphate precipitate that is then excreted in the feces.
## Primary Indications
* Management of hyperphosphatemia in patients with end-stage renal disease (ESRD).
## Adult Dosing
* **Initial Dose:** 667 mg to 1332 mg (equivalent to 1-2 grams of elemental calcium) administered orally with each meal.
* **Titration:** Dosage should be individualized based on serum phosphate levels. The goal is to maintain serum phosphate below 6 mg/dL. Doses can be increased in increments of 667 mg per meal as needed.
* **Maximum Dose:** Doses up to 3000 mg to 4000 mg (equivalent to 4.5-6 grams of elemental calcium) per day have been used, but higher doses increase the risk of hypercalcemia.
## Pediatric Dosing
* Dosing in pediatric patients is not well-established and should be individualized by a physician experienced in pediatric nephrology. Doses may range from 1332 mg to 2664 mg (2-4 grams) per day divided with meals, but careful monitoring for hypercalcemia is critical.
## Dose Adjustments
* **Renal Impairment:** Not applicable as it is used in patients with CKD. However, dose adjustments are often made based on serum calcium and phosphate levels.
* **Hepatic Impairment:** No specific dose adjustments are typically required.
## Contraindications
* Hypercalcemia.
* Hypersensitivity to calcium acetate.
* Concurrent use with medications that are affected by gastric pH changes (e.g., ketoconazole, itraconazole, digoxin) if adequate separation cannot be achieved.
## Adverse Effects
* **Common:** Hypercalcemia, constipation, nausea, vomiting, abdominal pain.
* **Serious:** Severe hypercalcemia (symptoms include confusion, lethargy, muscle weakness, constipation, anorexia, nausea, vomiting, polyuria, polydipsia, cardiac arrhythmias), metastatic calcification.
## Key Drug Interactions
* **Tetracyclines and Quinolones:** Calcium acetate can decrease the absorption of oral tetracyclines and fluoroquinolone antibiotics. Separate administration by at least 2 hours before and 4-6 hours after.
* **Digoxin:** Hypercalcemia from calcium acetate can potentiate digoxin toxicity.
* **Thyroid Hormones (Levothyroxine):** Calcium can reduce the absorption of levothyroxine. Separate administration by at least 4 hours.
* **Antacids (Aluminum and Magnesium-containing):** Concurrent use may increase the risk of aluminum toxicity.
## Monitoring
* **Serum Calcium:** Monitor regularly, especially when initiating or titrating therapy, and especially in patients taking vitamin D analogs.
* **Serum Phosphate:** Monitor regularly to assess efficacy and guide dosing.
* **Serum Magnesium and BUN:** Monitor periodically.
* **Signs and Symptoms of Hypercalcemia:** Educate patients and monitor for symptoms.
## Clinical Pearls
* Administer calcium acetate with meals to maximize its phosphate-binding capacity.
* The target serum phosphate level is generally less than 6 mg/dL.
* Hypercalcemia is the most common and serious side effect. Monitor calcium levels closely, particularly in patients also receiving vitamin D or its analogs.
* If hypercalcemia occurs, reduce the dose of calcium acetate or temporarily discontinue it.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information, drug compendia, or a qualified healthcare provider for specific treatment decisions, including dosing and safety considerations.
