Calcium Acetate

Approved Indications:

• Hyperphosphatemia in End-Stage Renal Disease (ESRD):
  Calcium acetate is primarily indicated to control serum phosphorus levels in patients with chronic kidney disease (CKD) on dialysis (hemodialysis or peritoneal dialysis). It helps reduce phosphate absorption from the gastrointestinal tract.

Off-Label / Clinically Accepted Uses:

• Secondary Hyperparathyroidism (as part of phosphate control)
• Adjunctive use in renal osteodystrophy when combined with dietary phosphate restriction.

Adults (Dialysis Patients):

• Initial dose: 1,334 mg orally with each meal (equivalent to 2 tablets of 667 mg or one capsule of 1,334 mg).
• Maintenance dose: Adjust by monitoring serum phosphorus. Most patients require 2–3 capsules/tablets with each meal.
• Maximum dose: Not well defined, but should be limited by serum calcium levels to avoid hypercalcemia.

Elderly:

• Same dosing as adults, but monitor serum calcium levels more frequently due to increased sensitivity to hypercalcemia.

Pediatric:

• Safety and efficacy not fully established in patients under 18 years.

Renal/Hepatic Impairment:

• Renal: Drug is indicated specifically for ESRD, but use cautiously in patients with residual kidney function to prevent hypercalcemia.
• Hepatic: No dose adjustment needed, but monitor if concurrent liver dysfunction exists.

Route of Administration:

• Oral (tablet, capsule, or oral solution form)
• Administer with meals to enhance phosphate binding.

Duration:

• Long-term therapy is required in dialysis patients; therapy is continued as long as hyperphosphatemia persists.

Calcium acetate acts as a phosphate binder in the gastrointestinal tract. Upon ingestion, calcium acetate dissociates to release calcium ions which bind to dietary phosphate to form insoluble calcium phosphate complexes. These are then excreted in the feces, thereby reducing phosphate absorption and serum phosphate levels. This mechanism helps manage hyperphosphatemia in patients with ESRD, reducing complications such as secondary hyperparathyroidism, vascular calcification, and bone disease.

• Absorption: Minimal systemic absorption of calcium occurs; phosphate is not absorbed due to precipitation.
• Bioavailability: Calcium absorption is approximately 30–40%, depending on vitamin D status and gastric pH.
• Distribution: Calcium is distributed in plasma (bound to albumin and in free form) and into bone tissues.
• Metabolism: Not metabolized; works locally in the GI tract.
• Elimination:
• Phosphate: Eliminated via feces as calcium phosphate complex.
• Calcium: Excess is excreted renally, though limited in ESRD patients.

• Pregnancy: Not assigned a formal FDA category. Use only if clearly needed. Excessive calcium intake may be harmful.
• Lactation: Calcium is excreted in human milk. Monitor maternal and infant serum calcium levels if used during breastfeeding.
• Recommendation: Use cautiously in pregnant or lactating women due to the risk of hypercalcemia in both mother and child.

• Primary Class: Phosphate Binder
• Sub-Class: Calcium-based Phosphate Binder

• Hypercalcemia
• Hypophosphatemia
• Known hypersensitivity to calcium acetate or any formulation component
• Severe hyperparathyroidism not adequately managed

• Risk of Hypercalcemia: Monitor serum calcium levels closely. Symptoms may include confusion, fatigue, arrhythmias.
• Calcium Load Risk: Cumulative calcium from diet, supplements, and binders may lead to vascular calcification.
• Drug Interactions: May interfere with absorption of other oral medications (e.g., iron, tetracyclines).
• Frequent Monitoring: Check serum phosphate and calcium levels at least biweekly at therapy initiation and during dosage adjustment.
• Avoid Concomitant Use with Other Calcium Products unless supervised.

Common:

• Gastrointestinal: Nausea, vomiting, constipation, dry mouth
• Metabolic: Hypercalcemia

Serious:

• Hypercalcemia-related complications: Confusion, arrhythmias, bone pain
• Vascular calcification: Long-term calcium overload may contribute to soft tissue calcification.

Rare:

• Hypophosphatemia (if overcorrected)
• Abdominal pain
• Pruritus

• Tetracyclines, Fluoroquinolones: Decreased absorption due to chelation with calcium.
• Levothyroxine: Reduced efficacy due to binding with calcium.
• Iron supplements: May reduce iron absorption when taken simultaneously.
• Digoxin: Hypercalcemia may increase risk of digitalis toxicity.

Interaction Mechanism:
Primarily through calcium ion chelation or competitive absorption in the gastrointestinal tract.

CYP450 Enzyme Involvement:
None known—drug acts locally and is not systemically metabolized.

• KDIGO Guidelines: Continue to recommend calcium acetate as a first-line phosphate binder in dialysis patients unless there's a risk of hypercalcemia.
• Shift Toward Non-Calcium Binders: In high-risk patients, newer guidelines suggest considering sevelamer or lanthanum for patients with persistent hypercalcemia.

• Temperature: Store at 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C–30°C.
• Humidity: Store in a dry place, away from moisture.
• Light Protection: Keep container tightly closed and protect from light.
• Handling Precautions: No need for refrigeration. Shake oral solution before use if applicable.
• Keep out of reach of children.