Calcium Carbonate

Approved Indications:

• Hypocalcemia: Treatment and prevention of calcium deficiency states.
• Osteoporosis: Adjunct in the management and prevention of osteoporosis, including postmenopausal, age-related, and corticosteroid-induced.
• Rickets and Osteomalacia: Supportive therapy in vitamin D-deficient conditions.
• Chronic Renal Failure: Management of secondary hyperparathyroidism and phosphate binding to control hyperphosphatemia.
• Antacid: Temporary relief of symptoms of indigestion, heartburn, and upset stomach.
• Pregnancy & Lactation Support: As a dietary calcium supplement to support maternal and fetal bone health.
• Growth Support: In adolescents during growth spurts where dietary intake may be insufficient.

Clinically Accepted Off-label Uses:

• Premenstrual Syndrome (PMS): Symptom relief in women with PMS.
• Colorectal Cancer Prevention: As a dietary supplement in long-term prevention strategies.
• Calcium Oxalate Nephrolithiasis: Used with thiazide diuretics and dietary modifications for kidney stone prevention.

Adults:

• Supplementation (osteoporosis, dietary deficiency): 500 mg to 1500 mg elemental calcium per day, in 1–3 divided doses.
• Antacid use: 500 mg to 1,000 mg as needed, up to 7,000 mg/day.
• Hyperphosphatemia in CKD: 1,500 mg to 3,000 mg/day elemental calcium in divided doses with meals.

Pediatrics:

• Children (1–8 years): 500 mg to 800 mg/day elemental calcium.
• Adolescents (9–18 years): 1,000 mg to 1,300 mg/day elemental calcium.
• Dose should be adjusted according to age, weight, and serum calcium levels.

Elderly:

• 1,000 mg to 1,200 mg/day elemental calcium, with attention to renal function and constipation risk.

Pregnancy & Lactation:

• 1,000 mg/day (pregnant women <18 years may require up to 1,300 mg/day).

Renal/Hepatic Impairment:

• Use with caution; dose adjustment may be required due to risk of hypercalcemia and calcium accumulation in renal impairment.

Route of Administration:

• Oral: Tablet, chewable tablet, liquid suspension, or powder.
• To enhance absorption, administer with meals. Avoid simultaneous intake with iron, tetracyclines, or quinolones.

Calcium Carbonate provides elemental calcium, a vital component for various physiological processes, including bone mineralization, muscle contraction, nerve function, and blood clotting. As an antacid, it neutralizes gastric hydrochloric acid by releasing calcium ions, forming calcium chloride, carbon dioxide, and water, thereby relieving hyperacidity. In chronic kidney disease, calcium carbonate acts as a phosphate binder by forming insoluble calcium phosphate salts in the gut, reducing serum phosphate levels.

• Absorption: Approximately 30% of elemental calcium is absorbed from the GI tract, enhanced by vitamin D and acidic pH.
• Distribution: Widely distributed; over 99% found in bones and teeth.
• Metabolism: Not metabolized; ionic calcium enters systemic circulation.
• Excretion: Excreted primarily in the feces (unabsorbed fraction); absorbed calcium is excreted renally.
• Onset of Action: Antacid effect within 15–30 minutes.
• Peak Plasma Time: 1.3 to 2 hours post-dose.
• Elimination Half-life: Not applicable (elemental ion).
• Bioavailability: Variable (15%–45%) depending on gastric pH, vitamin D levels, and formulation.

• Pregnancy: Considered safe during pregnancy at recommended dietary intakes. Excessive intake may pose a risk of maternal hypercalcemia and fetal complications.
• Lactation: Excreted in breast milk in small amounts. Generally regarded as safe when used within recommended limits.
• Caution: Monitor total calcium intake to avoid cumulative toxicity, especially if combined with other supplements or vitamin D.

• Primary Class: Calcium Supplement
• Subclass: Antacid / Phosphate Binder / Bone Mineral Supplement

• Hypersensitivity to calcium carbonate or any excipient
• Hypercalcemia (e.g., hyperparathyroidism, vitamin D intoxication)
• Severe renal impairment or renal calculi
• Hypophosphatemia (unless used with phosphate supplementation)
• Zollinger-Ellison Syndrome (long-term antacid use may mask symptoms)

• Monitor for hypercalcemia in patients with renal dysfunction or those on high vitamin D intake.
• Use with caution in elderly due to constipation risk.
• May interfere with absorption of other medications (e.g., iron, levothyroxine, tetracyclines).
• Avoid excessive doses to prevent milk-alkali syndrome.
• Periodically monitor serum calcium, phosphate, and renal function in chronic use.

Common:

• Gastrointestinal: Constipation, bloating, flatulence, nausea
• Antacid use: Belching due to CO₂ release

Less Common:

• Hypercalcemia (symptoms: confusion, muscle weakness, arrhythmias)
• Nephrolithiasis (renal stones)

Rare/Serious:

• Milk-alkali syndrome (hypercalcemia, metabolic alkalosis, renal impairment)
• Abdominal pain, vomiting
• Hypophosphatemia (with long-term use)

• Decreased Absorption of Other Drugs:
• Iron supplements, tetracyclines, fluoroquinolones (separate by 2–4 hours)
• Bisphosphonates, thyroid hormones (e.g., levothyroxine)
• Increased Calcium Levels:
• Vitamin D, thiazide diuretics, lithium (additive hypercalcemia risk)
• CYP Enzyme Systems:
• Not significantly involved in CYP450 metabolism
• Food Interactions:
• High-oxalate and high-phytate foods (e.g., spinach, bran) may reduce absorption

• Guideline Emphasis:
• Recent bone health guidelines emphasize optimal intake of calcium and vitamin D for osteoporosis prevention.
• Revised Dosage Guidance:
• New recommendations encourage dietary sources over supplementation unless clinically indicated.
• FDA Advisories:
• Caution advised against routine high-dose calcium supplementation due to cardiovascular and renal risks in some populations.

• Storage Temperature: Store at 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C–30°C.
• Light & Moisture: Protect from moisture and excessive heat. Store in tightly closed containers.
• Handling: Keep out of reach of children. Do not use if tablets are discolored or chipped.
• Liquid Formulations: Shake well before use. Refrigeration is not necessary unless specified by manufacturer.