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# Calcium Acetate
## Overview
Calcium acetate is a phosphate binder used to control hyperphosphatemia in patients with chronic kidney disease (CKD). It works by binding to dietary phosphate in the gastrointestinal tract, forming insoluble calcium phosphate, which is then excreted in the feces.
## Primary Indications
* Treatment of hyperphosphatemia in patients with end-stage renal disease (ESRD).
## Adult Dosing
* **Starting Dose:** 667 mg (equivalent to 169 mg elemental calcium or 13.3 mEq calcium) orally three times daily with meals.
* **Titration:** Dosage should be individualized based on serum phosphate levels.
* **Maximum Dose:** Generally, no specific maximum is established, but doses exceeding 4000 mg/day (approximately 2500 mg elemental calcium) are rarely needed and increase the risk of hypercalcemia. Doses should be guided by serum phosphate and calcium levels.
## Pediatric Dosing
* Dosing in pediatric patients is not well-established and should be individualized based on clinical response and laboratory parameters, with close monitoring for hypercalcemia and aluminum toxicity (if aluminum-containing antacids are used concurrently).
* A common starting point is 10-15 mg/kg/day of elemental calcium given in divided doses with meals.
## Dose Adjustments
* **Renal Impairment:** Not applicable as it is primarily used in patients with ESRD.
* **Hepatic Impairment:** No specific adjustments are typically needed.
* **Adjustments based on Labs:** Dosage must be titrated based on serum phosphate and calcium levels. Target serum phosphate is typically less than 6 mg/dL.
## Contraindications
* Hypercalcemia.
* Hypersensitivity to calcium acetate.
* Conditions leading to hypercalcemia, such as metastatic bone disease or certain granulomatous diseases.
## Adverse Effects
* **Common:** Hypercalcemia, constipation, nausea, vomiting, anorexia, dry mouth.
* **Less Common:** Hypersensitivity reactions.
* **Serious:** Severe hypercalcemia, which can lead to cardiac arrhythmias, confusion, stupor, coma, and acute kidney injury.
## Key Drug Interactions
* **Tetracyclines and Fluoroquinolones:** Calcium acetate can decrease the absorption of these antibiotics. Administer at least 2 hours before or 6 hours after calcium acetate.
* **Thyroid Hormones (e.g., Levothyroxine):** Calcium can impair the absorption of thyroid hormones. Separate administration by at least 4 hours.
* **Biphosphonates:** Calcium can decrease the absorption of biphosphonates. Separate administration by at least 2 hours.
* **Digitalis Glycosides:** Hypercalcemia can increase the risk of digitalis toxicity. Monitor closely.
* **Thiazide Diuretics:** May increase the risk of hypercalcemia.
## Monitoring
* **Serum Phosphate:** Monitor regularly to guide dosage adjustments.
* **Serum Calcium:** Monitor frequently, especially when initiating therapy or increasing the dose. Target serum calcium levels are usually between 8.5-10 mg/dL, though this may vary based on institutional protocol and patient-specific factors.
* **Serum Magnesium and Alkaline Phosphatase:** Monitor periodically.
## Clinical Pearls
* Calcium acetate must be taken with meals to be effective in binding dietary phosphate.
* Patients should be educated on the signs and symptoms of hypercalcemia (e.g., nausea, vomiting, constipation, abdominal pain, increased thirst and urination, confusion).
* The risk of hypercalcemia is increased in patients taking vitamin D supplements or those with underlying conditions predisposing to hypercalcemia.
* Consider the elemental calcium content of calcium acetate when calculating total daily elemental calcium intake to avoid exceeding recommended limits. Each 667 mg tablet contains approximately 169 mg of elemental calcium.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional guidelines before making clinical decisions.*
