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# Calcium Acetate
## Overview
Calcium acetate is a phosphate binder used to reduce serum phosphorus levels in patients with hyperphosphatemia, typically associated with chronic kidney disease (CKD). It works by binding to dietary phosphate in the gastrointestinal tract, forming insoluble calcium phosphate that is then excreted in the feces.
## Primary Indications
* Treatment of hyperphosphatemia in patients with end-stage renal disease (ESRD).
## Adult Dosing
The dose of calcium acetate should be individualized based on serum phosphorus levels.
* **Starting dose:** Typically 667 mg (equivalent to 13.3 mEq elemental calcium) administered orally with each meal.
* **Titration:** Doses can be increased as needed to achieve target serum phosphorus levels. Doses may be given with snacks.
* **Maximum dose:** While not strictly defined, doses up to 1334 mg (26.6 mEq elemental calcium) per meal are common. Higher doses may increase the risk of hypercalcemia.
* **Typical total daily dose:** May range from 2001 mg to 4002 mg (40-80 mEq elemental calcium) or higher, divided with meals.
## Pediatric Dosing
Dosing in pediatric patients is not well-established and should be determined by a pediatric nephrologist. Dosing is typically based on age and weight, with careful monitoring for efficacy and adverse effects.
## Dose Adjustments
* **Renal Impairment:** Calcium acetate is primarily indicated for patients with significant renal impairment (CKD/ESRD). Dose adjustments are driven by serum phosphorus and calcium levels.
* **Hepatic Impairment:** No specific dose adjustments are typically required.
## Contraindications
* Hypercalcemia.
* Hypersensitivity to calcium acetate.
* Certain conditions that predispose to hypercalcemia, such as metastatic bone disease or primary hyperparathyroidism.
## Adverse Effects
* **Common:** Hypercalcemia (most significant concern), constipation, nausea, vomiting, abdominal pain.
* **Serious:** Severe hypercalcemia can lead to cardiac arrhythmias, confusion, lethargy, coma, renal calcification, and vascular calcification.
## Key Drug Interactions
* **Tetracyclines and Quinolones:** Calcium acetate can decrease the absorption of these antibiotics. Administer these agents at least 2 hours before or 6 hours after calcium acetate.
* **Levothyroxine:** Calcium acetate can decrease the absorption of levothyroxine. Separate administration by at least 4 hours.
* **Digitalis glycosides:** Hypercalcemia can increase the risk of digitalis toxicity.
* **Thiazide diuretics:** May increase the risk of hypercalcemia.
* **Antacids containing calcium or magnesium:** Concurrent use may lead to excessive calcium or magnesium intake.
## Monitoring
* **Serum Phosphorus:** Monitor regularly (e.g., every 1-2 weeks initially, then monthly) to assess efficacy and guide dosing.
* **Serum Calcium:** Monitor regularly (e.g., before initiating therapy, within the first month, and then every few months) to prevent or detect hypercalcemia. Target serum calcium should be within the laboratory's normal range or as per institutional protocol.
* **Electrolytes:** Monitor other electrolytes as clinically indicated.
## Clinical Pearls
* Calcium acetate must be taken with meals to effectively bind dietary phosphate.
* The goal is to control serum phosphorus levels while avoiding hypercalcemia. The product of serum calcium and serum phosphorus should ideally be < 55 mg²/dL².
* Patients with ESRD are prone to both hyperphosphatemia and hypercalcemia; careful monitoring is crucial.
* Consider alternative phosphate binders if hypercalcemia is difficult to manage.
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*Disclaimer: This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and institutional protocols for definitive guidance.*
