Drug information of Calcium carbonate

Calcium carbonate

Calcium carbonate is a dietary supplement used when the amount of calcium taken in the diet is not enough. Calcium is needed by the body for healthy bones, muscles, nervous system, and heart. Calcium carbonate also is used as an antacid to relieve heartburn, acid indigestion, and upset stomach.

 Calcium carbonate is a basic compound that acts by neutralizing hydrochloric acid in gastric secretions. Subsequent increases in pH may inhibit the action of pepsin. An increase in bicarbonate ions and prostaglandins may also confer cytoprotective effects.

Mechanism of effect

As dietary supplement, used to prevent or treat negative calcium balance; in osteoporosis, it helps to prevent or decrease the rate of bone loss. Calcium is an integral component of the skeleton and also moderates nerve and muscle performance and allows normal cardiac function. Also used to treat hyperphosphatemia in patients with chronic kidney disease by combining with dietary phosphate to form insoluble calcium phosphate, which is excreted in feces. Calcium salts as antacids neutralize gastric acidity resulting in increased gastric and duodenal bulb pH.


Gastric-peptic disease occurs as a result of an imbalance between protective factors, such as mucus, bicarbonate, and prostaglandin secretion, and aggressive factors, such as hydrochloric acid, pepsin, and Helicobacter pylori (H. pylori).
Antacids work by restoring acid-base balance, attenuating the pepsin activity and increasing bicarbonate and prostaglandin secretion. The acid-neutralizing capacity of calcium carbonate is 58 mEq/15 ml. When used as a nutritional supplement, calcium carbonate acts by directly increasing calcium stores within the body.


Absorption: Minimal unless chronic, high doses; absorption predominantly in the duodenum and dependent on calcitriol and vitamin D; mean absorption of calcium intake varies with age (infants 60%, prepubertal children 28%, pubertal children 34%, adults 25%); during pregnancy, calcium absorption doubles; calcium is absorbed in soluble, ionized form; solubility of calcium is increased in an acid environment; decreased absorption occurs in patients with achlorhydria, steatorrhea, or uremia

Distribution: Primarily in bones, teeth.

Protein binding: ~40%, primarily to albumin.

Excretion: Primarily feces (75%; as unabsorbed calcium); urine (22%).



Take at onset of GI distress

500 mg: 2-4 tablets; not to exceed 15 tabs/24 hr

750 mg: 2-4 tablets; not to exceed 10 tabs/24 hr

1000 mg: 2-3 tablets; not to exceed 7 tabs/24 hr

Calcium Supplementation

1-1.2 g PO qDay or divided q6-12hr with meals

Recommended Dietary Allowance

19-50 years: 1 g/day PO


>51 years: 1.2 g/day PO


51-70 years: 1 g/day PO

>71 years: 1.2 g/day PO

Dosing Considerations

(Calcium carbonate (elemental calcium equivalent

(400 mg (161 mg

(500 mg (200 mg

(750 mg (300 mg

(1000 mg (400 mg


Treatment of hyperphosphatemia in patients with end-stage renal disease


Concerns related to adverse effects:

Gastrointestinal effects: Constipation, bloating, and gas are common with calcium supplements (especially carbonate salt).

Hypercalcemia: Chronic hypercalcemia may result in vascular calcification and other soft-tissue calcification.

Disease-related concerns:

Achlorhydria: Calcium absorption is impaired in achlorhydria; administration is followed by increased gastric acid secretion within 2 hours of administration especially with high doses. Common in the elderly, use an alternate salt (eg, citrate) and administer with food.

Hypoparathyroid disease: Hypercalcemia and hypercalciuria are most likely to occur in hypoparathyroid patients receiving high doses of vitamin D.

Kidney stones (calcium-containing): Use caution when administering calcium supplements to patients with a history of kidney stones.

Renal insufficiency: Use with caution as these patients are more sensitive or susceptible to the effects of excess calcium.

Concurrent drug therapy issues:

Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment. Consult drug interactions database for more detailed information.

Vitamin D: It is recommended to concomitantly administer vitamin D for optimal calcium absorption when used for the treatment or prevention of conditions related to bone health (eg, osteoporosis).

Other warnings/precautions:

Appropriate product selection: Multiple salt forms of calcium exist; close attention must be paid to the salt form when ordering and administering calcium; incorrect selection or substitution of one salt for another without proper dosage adjustment may result in serious over or under dosing.

Points of recommendation

  • Discuss specific use of drug and side effects with patient as it relates to treatment.
  • Have patient report immediately to prescriber severe constipation.
  • Food may increase calcium absorption. Calcium may decrease iron absorption. Bran, foods high in oxalates, or whole grain cereals may decrease calcium absorption. Management: Administer with food.

Ask a Pharmacist

User's questions
    No comments yet.