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# Calcium acetate
## Overview
Calcium acetate is a potent phosphate binder used primarily in patients with end-stage renal disease (ESRD). It dissociates in the gut, where the calcium ion binds to dietary phosphate to form insoluble calcium phosphate, which is then excreted in the feces. It provides a higher calcium-to-phosphate binding ratio compared to calcium carbonate.
## Primary Indications
* Hyperphosphatemia in patients with end-stage renal disease (ESRD).
## Adult Dosing
* **Initial:** 1,334 mg (two 667 mg capsules/tablets) orally with each meal.
* **Titration:** Adjust based on serum phosphate levels. Most patients require 2,000 mg to 4,000 mg per day.
* **Maximum:** Generally avoid exceeding 12,000 mg/day (equivalent to ~3,000 mg of elemental calcium) due to risks of hypercalcemia. Specific titration protocols vary by institution.
## Pediatric Dosing
* **Dosing:** Not well-established. Data is limited.
* **Clinical Note:** Use is off-label and requires nephrology consultation. Dosing is typically individualized based on serum phosphate levels and dietary intake. Use with extreme caution due to the risk of iatrogenic hypercalcemia and metastatic calcification.
## Dose Adjustments
* **Renal Impairment:** Required; specifically designed for patients with ESRD (hemodialysis/peritoneal dialysis).
* **Hepatic Impairment:** No specific adjustment required.
## Contraindications
* Hypercalcemia.
* Hypophosphatemia.
* Nephrolithiasis (calcium-containing stones).
## Adverse Effects
* **Common:** Hypercalcemia, nausea, vomiting, constipation, and abdominal pain.
* **Serious:** Metastatic calcification (soft tissue/vascular), cardiovascular events, and cardiac arrhythmias (if hypercalcemia is severe).
## Key Drug Interactions
* **Fluoroquinolones/Tetracyclines:** Calcium significantly decreases absorption. Separate administration by at least 2–4 hours.
* **Levothyroxine:** Calcium interferes with thyroid hormone absorption; separate by at least 4 hours.
* **Bisphosphonates:** Calcium reduces bisphosphonate absorption; administer at least 2 hours apart.
* **Vitamin D Products:** Increased risk of hypercalcemia when used concurrently.
## Monitoring
* **Serum Calcium:** Monitor weekly during dose titration and periodically thereafter.
* **Serum Phosphate:** Monitor phosphorus levels to ensure effective binding and to prevent overtreatment.
* **Calcium-Phosphate Product:** Maintain the product (Ca × P) below 55 mg²/dL² to reduce the risk of extraskeletal calcification.
* **Symptoms of Hypercalcemia:** Monitor for confusion, constipation, polyuria, or cardiac irregularities.
## Clinical Pearls
* **Timing:** Must be taken with meals to maximize contact with dietary phosphate. If a meal is missed, the dose should be skipped.
* **Elemental Calcium:** 667 mg of calcium acetate provides approximately 169 mg of elemental calcium.
* **Hypercalcemia Risk:** Calcium-based binders should be used with caution in patients with high serum calcium or those receiving high doses of Vitamin D analogs. Switch to non-calcium-based binders (e.g., sevelamer, lanthanum) if hypercalcemia persists.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice protocols and drug labeling can change. Always verify current prescribing information, institutional guidelines, and patient-specific factors before administering any medication.
