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# Calcium Acetate
## Overview
Calcium acetate is a phosphate binder used primarily in patients with end-stage renal disease (ESRD). It acts by binding dietary phosphate in the gastrointestinal tract 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 and is less dependent on gastric pH.
## Primary Indications
* Hyperphosphatemia in patients with end-stage renal disease (ESRD).
## Adult Dosing
* **Initial Dose:** 1,334 mg (2 capsules/tablets) orally with each meal.
* **Titration:** Dosage should be titrated based on serum phosphate levels.
* **Maintenance:** Generally ranges from 1,334 mg to 2,668 mg per meal. Clinical response dictates the frequency and dose; exceeding 2,668 mg per meal is generally not recommended due to the risk of hypercalcemia.
## Pediatric Dosing
* **Dosing:** Not well-established. If used, dosing is off-label and requires nephrology consultation.
* **General Approach:** Usually initiated at 20–50 mg/kg/day (of elemental calcium) divided with each meal, titrated to serum phosphate targets. Local institutional protocols must be consulted.
## Dose Adjustments
* **Renal Impairment:** Used specifically for ESRD; no dose reduction required for renal function, but monitor serum calcium frequently.
* **Hypercalcemia:** Reduce dose or temporarily discontinue if serum calcium levels become elevated or if the calcium-phosphate product exceeds 55 mg²/dL².
## Contraindications
* Hypercalcemia.
* Hypophosphatemia.
* Known hypersensitivity to calcium acetate or excipients.
## Adverse Effects
* **Common:** Nausea, vomiting, constipation, abdominal pain.
* **Serious:** Hypercalcemia, metastatic soft tissue calcification, pruritus, vascular calcification.
## Key Drug Interactions
* **Fluoroquinolones/Tetracyclines:** Impairs absorption. Administer at least 2 hours before or 6 hours after calcium acetate.
* **Bisphosphonates:** Calcium reduces absorption. Take at least 2 hours apart.
* **Levothyroxine:** Oral absorption may be reduced. Separate administration by at least 4 hours.
* **Iron Supplements:** Concurrent use decreases iron absorption; separate by 2–3 hours.
## Monitoring
* **Serum Phosphate:** Monitor every 2–4 weeks initially, then periodically.
* **Serum Calcium:** Monitor weekly during initiation and dose titration; monitor monthly thereafter.
* **Calcium-Phosphate Product:** Maintain <55 mg²/dL².
* **Symptoms:** Monitor for signs of hypercalcemia (nausea, vomiting, confusion, cardiac arrhythmias).
## Clinical Pearls
* **Administration Timing:** Must be taken with meals to maximize phosphate binding. If a dose is missed, omit it; do not double the dose.
* **Elemental Calcium:** Each 667 mg calcium acetate capsule/tablet provides 169 mg of elemental calcium.
* **Hypercalcemia Risk:** Monitor closely if the patient is also taking vitamin D analogs or high-calcium dialysate, as these significantly increase the risk of hypercalcemia.
* **Non-calcium binders:** Consider switching to sevelamer or lanthanum if hypercalcemia develops or if the patient is at high risk for vascular calcification.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice varies by institution. Always verify dosages, contraindications, and drug interactions through official prescribing information (package insert) and current clinical decision support tools before prescribing or administering medication.
