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# Calcium Acetate
## Overview
Calcium acetate is a phosphate binder used to reduce serum phosphorus levels in patients with hyperphosphatemia. It dissociates in the gastrointestinal tract releasing calcium ions and acetate ions. The calcium binds to dietary phosphate, forming insoluble calcium phosphate, which is then excreted in the feces.
## Primary Indications
* Management of hyperphosphatemia in patients with chronic kidney disease (CKD) on dialysis.
## Adult Dosing
The goal is to lower serum phosphorus to target levels, typically below 6 mg/dL. Dosing is highly individualized and depends on dietary phosphorus intake and serum phosphorus levels.
* **Initial Dose:** 667 mg (13.3 mEq calcium) orally with each meal.
* **Titration:** Dosage should be adjusted based on serum phosphorus levels. Doses can be increased by 667 mg per meal increments.
* **Maximum Dose:** Generally considered up to 4000 mg (80 mEq calcium) per day, divided among meals. However, patient-specific titration is paramount, and exceeding this may be necessary under close supervision to achieve phosphorus control.
## Pediatric Dosing
Dosing in pediatric patients is not well-established and should be based on institutional protocols and specialist recommendations. Titration should be guided by serum phosphorus levels and calcium-phosphorus product.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Patients with CKD already have impaired calcium and phosphate handling. Monitor calcium levels closely.
* **Hepatic Impairment:** No specific dose adjustment is typically required, but monitor calcium levels.
## Contraindications
* Hypercalcemia.
* Hypersensitivity to calcium acetate.
* Concurrent use with medications that can cause hypercalcemia (e.g., thiazide diuretics, vitamin D analogues) should be approached with caution.
## Adverse Effects
* **Hypercalcemia:** Most common and serious adverse effect. Symptoms include constipation, nausea, vomiting, abdominal pain, dry mouth, anorexia, polyuria, polydipsia, fatigue, and cardiac arrhythmias.
* **Gastrointestinal:** Constipation, nausea, diarrhea.
* **Other:** Headache, abdominal distension, increased thirst.
## Key Drug Interactions
* **Tetracyclines and Quinolone Antibiotics:** Calcium acetate can decrease the absorption of these drugs. Separate administration by at least 2 hours before or 6 hours after calcium acetate.
* **Thyroid Hormones (Levothyroxine):** Calcium acetate can reduce the absorption of levothyroxine. Separate administration by at least 4 hours.
* **Bisphosphonates:** Concurrent use can increase the risk of hypocalcemia.
* **Digoxin:** Hypercalcemia can increase the risk of digoxin toxicity.
* **Thiazide Diuretics:** May increase the risk of hypercalcemia.
* **Vitamin D Analogues:** May increase the risk of hypercalcemia.
## Monitoring
* **Serum Phosphorus:** Monitor frequently (e.g., weekly or bi-weekly) until phosphorus levels are stabilized within the target range, then monitor monthly.
* **Serum Calcium:** Monitor frequently, especially when initiating or adjusting dose. Target serum calcium levels should generally be maintained within the normal range or slightly above, but *avoiding* hypercalcemia.
* **Calcium-Phosphorus Product (Ca x P):** Monitor to avoid levels > 55 mg²/dL² due to increased risk of soft tissue calcification.
* **Alkaline Phosphatase:** May be monitored periodically in patients with CKD.
## Clinical Pearls
* Administer calcium acetate with meals to effectively bind dietary phosphate.
* Dosage must be individualized based on serum phosphorus levels and dietary intake.
* Vigilant monitoring for hypercalcemia is crucial. If hypercalcemia occurs, discontinue calcium acetate and reduce calcium and vitamin D intake.
* The goal of therapy is to reduce serum phosphorus and the calcium-x-phosphorus product, not necessarily to normalize serum calcium.
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*Please verify current prescribing information and institutional protocols before use.*
