Calcium Acetate

Usage

• Calcium acetate is primarily prescribed to reduce serum phosphorus levels in patients with end-stage renal disease (ESRD) who are on dialysis. Elevated phosphorus levels in these patients can lead to complications such as ectopic calcification and secondary hyperparathyroidism. It is also used as a calcium supplement.
• Pharmacological Classification: Phosphate binder, calcium supplement.
• Mechanism of Action: Calcium acetate binds to dietary phosphate in the gut, forming insoluble calcium phosphate which is then excreted in the feces, thereby reducing phosphate absorption into the bloodstream.

Alternate Names

• Other names: Calcium diacetate, calcium ethanoate
• Brand names: PhosLo, Phoslyra, Calphron, Eliphos.

How It Works

• Pharmacodynamics: Calcium acetate lowers serum phosphate levels by binding to phosphate in the gastrointestinal tract, preventing its absorption. This action helps maintain calcium-phosphate balance in ESRD patients. It also works as a calcium supplement to prevent or treat negative calcium balance.

• Pharmacokinetics:

  • Absorption: Orally administered calcium acetate is absorbed systemically, with absorption influenced by factors like vitamin D levels and the presence of food in the GI tract. Absorption is generally around 30% to 40%.
  • Metabolism: Acetate, a component of calcium acetate, is metabolized to bicarbonate.
  • Elimination: Unabsorbed calcium and the insoluble calcium phosphate complex are eliminated in the feces. Absorbed calcium is excreted primarily by the kidneys.

• Mode of Action: Calcium acetate acts by chemical binding within the intestinal lumen. It does not involve receptor binding, enzyme inhibition, or neurotransmitter modulation.

• Elimination Pathways: Primarily fecal excretion of unabsorbed calcium and calcium phosphate. Renal excretion of absorbed calcium.

Dosage

Standard Dosage

Adults:

• Initial: 1334 mg (2 tablets/capsules or 10 mL oral solution) with each meal.
• Maintenance: Titrate dose every 2-3 weeks up to a usual dose of 2001-2668 mg (3-4 tablets/capsules or 15-20 mL oral solution) with each meal, based on serum phosphorus levels and to avoid hypercalcemia.

Children:

• Safety and efficacy have not been established in pediatric patients under 18 years old.

Special Cases:

• Elderly Patients: Initiate therapy at the lower end of the dosing range and titrate cautiously due to potential age-related decrease in hepatic, renal, or cardiac function.
• Patients with Renal Impairment: Calcium acetate is used in patients with ESRD requiring dialysis; dose adjustments are based on serum phosphorus and calcium levels.
• Patients with Hepatic Dysfunction: No specific dosage adjustments are indicated, but monitor for side effects.
• Patients with Comorbid Conditions: Monitor closely for drug interactions and adjust dosages accordingly. Patients with sarcoidosis or receiving cardiac glycosides require careful monitoring due to the risk of hypercalcemia exacerbating existing conditions.

Clinical Use Cases

• Calcium acetate is not indicated for use in clinical settings like intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations. Its primary use is for chronic management of hyperphosphatemia in ESRD.

Dosage Adjustments

• Adjust dosage based on serum phosphorus and calcium levels. Decrease or discontinue if hypercalcemia develops.

Side Effects

Common Side Effects

• Nausea, vomiting, constipation, hypercalcemia.

Rare but Serious Side Effects

• Severe hypercalcemia leading to confusion, delirium, stupor, and coma.

Long-Term Effects

• Soft tissue calcification, vascular calcification (with prolonged hypercalcemia).

Adverse Drug Reactions (ADR)

• Hypercalcemia requiring dosage reduction or discontinuation, especially if severe.

Contraindications

• Hypercalcemia, hypersensitivity to calcium acetate.

Drug Interactions

• Calcium acetate can decrease the absorption of various medications, including tetracycline antibiotics, fluoroquinolones, bisphosphonates, thyroid medications, and iron supplements. Administer these medications at least 1 hour before or 3 hours after calcium acetate.
• Monitor for increased risk of digitalis toxicity with concomitant use of cardiac glycosides.
• Avoid concomitant use of calcium supplements.

Pregnancy and Breastfeeding

• Pregnancy Safety Category: C
• Fetal Risks: Maternal hypercalcemia can lead to complications such as stillbirth, preterm delivery, and neonatal hypocalcemia. Close monitoring of serum calcium is essential if calcium acetate is used during pregnancy.
• Breastfeeding: Calcium acetate is excreted in breast milk. Monitor the infant for potential adverse effects if the mother is taking this medication.

Drug Profile Summary

• Mechanism of Action: Binds phosphate in the gut, reducing absorption.
• Side Effects: Nausea, vomiting, constipation, hypercalcemia.
• Contraindications: Hypercalcemia.
• Drug Interactions: Tetracyclines, fluoroquinolones, bisphosphonates, iron, thyroid medications.
• Pregnancy & Breastfeeding: Use with caution; monitor serum calcium levels closely.
• Dosage: Initial: 1334 mg with meals, titrate up to 2668 mg with meals.
• Monitoring Parameters: Serum phosphorus, serum calcium.

Popular Combinations

• Calcium acetate is typically not used in combination with other phosphate binders containing calcium. However, non-calcium-based phosphate binders might be necessary in some situations to adequately control hyperphosphatemia without inducing hypercalcemia.

Precautions

• General Precautions: Monitor serum calcium levels regularly, especially during initial dosage titration. Assess dietary calcium intake.
• Specific Populations: Use with caution in pregnancy and breastfeeding. Safety and effectiveness in pediatric patients have not been established. Geriatric patients require careful dosage titration.
• Lifestyle Considerations: Patients should limit oxalate-rich foods to avoid calcium oxalate formation.

FAQs (Frequently Asked Questions)

Q1: What is the recommended dosage for Calcium Acetate?

A: Adults: Initial dose is 1334 mg with each meal. Titrate up to 2001-2668 mg per meal based on serum phosphorus and to avoid hypercalcemia. Pediatric: safety and efficacy have not been established.

Q2: What is the primary use of Calcium Acetate?

A: It is used to lower serum phosphate levels in patients with end-stage renal disease (ESRD) on dialysis.

Q3: How does Calcium Acetate work?

A: It binds to dietary phosphate in the gut, forming insoluble calcium phosphate that is then excreted, thus reducing phosphate absorption.

Q4: What are the common side effects of Calcium Acetate?

A: Nausea, vomiting, constipation, and hypercalcemia.

Q5: Are there any serious side effects I should be aware of?

A: Yes, severe hypercalcemia can occur, leading to serious neurological symptoms. Monitor serum calcium closely.

Q6: Can Calcium Acetate be used during pregnancy?

A: It should be used cautiously during pregnancy only if the benefits outweigh the potential risks to the fetus. Maintain normal maternal calcium levels.

Q7: Does Calcium Acetate interact with other medications?

A: Yes, it can interfere with the absorption of several drugs, including tetracycline antibiotics, fluoroquinolones, bisphosphonates, and iron supplements.

Q8: What should I monitor in patients taking Calcium Acetate?

A: Serum calcium and phosphorus levels should be monitored regularly.

Q9: Are there any contraindications for Calcium Acetate?

A: Yes, hypercalcemia is a contraindication.

Q10: What happens in case of an overdose of Calcium Acetate?

A: Overdose can lead to hypercalcemia. Treatment involves discontinuation of calcium acetate and management of the elevated calcium levels.