Calcium carbonate

• BPCalcium Carbonate
• JPPrecipitated Calcium Carbonate
• Ph. Eur.Calcium Carbonate
• USP–NFCalcium Carbonate

Calcii carbonas; calcium carbonate, precipitated; precipitated chalk; Destab; Millicarb; Omyapure; Pharma-Carb; Vivapress Ca; E170

Carbonic acid, calcium salt (1:1) · [471-34-1]

UNII H0G9379FGK · PubChem CID 10112

CaCO3 · 100.09

Diluent (filler), pH adjuster, buffering agent

Typical concentrations: — · Dosage forms: Solid

Used as a diluent in tablets and capsules (special granulated grades are made for direct compression), as a base for chewable and medicated confectionery tablets, as a buffering and dissolution aid, and as an opacifier and white colour in coatings. It is also used therapeutically as an antacid and calcium supplement, in which case it may make up most of the tablet weight, and as a food additive.

A white, odourless and tasteless powder or crystals. Precipitated grades consist of fine particles; ground grades are produced from natural limestone or chalk.

Crystal forms

calcite (rhombohedral, the stable form) and aragonite (orthorhombic)

True density

≈ 2.7 g/cm³ (calcite)

Thermal behaviour

decomposes above about 800 °C to calcium oxide and carbon dioxide

Solubility

practically insoluble in water and ethanol; solubility in water is increased by carbon dioxide and ammonium salts; dissolves with effervescence in dilute acids

pH

≈ 9 (saturated aqueous suspension)

Chemically stable. Store in a well-closed container in a cool, dry place.

Reacts with acids and ammonium salts with release of carbon dioxide, and can raise the microenvironmental pH of formulations containing acid-labile drugs. Calcium ions reduce the absorption of drugs such as tetracyclines and fluoroquinolones by forming complexes.

Precipitated calcium carbonate is made by passing carbon dioxide through a suspension of calcium hydroxide (from calcined limestone), or by reacting calcium chloride with sodium carbonate in solution. Ground calcium carbonate is obtained by milling and classifying purified natural limestone or chalk.

Regarded as non-toxic at excipient levels. At therapeutic antacid doses it may cause constipation and acid rebound, and prolonged high intake, especially with milk or other alkalis, can lead to hypercalcaemia and milk-alkali syndrome.

Observe normal precautions for the quantity handled. The dust may irritate the eyes and respiratory tract; eye protection, gloves and a dust mask are recommended.

GRAS listed. Accepted as a food additive in Europe (E170). Included in the FDA Inactive Ingredient Database (oral capsules, tablets and other oral preparations) and in non-parenteral medicines licensed in Europe.

Calcium phosphate, dibasic; calcium phosphate, tribasic; calcium sulfate; magnesium carbonate.

Plain powdered calcium carbonate compresses poorly, so direct-compression grades are granulated with a small amount of binder. Its high density allows compact high-dose calcium tablets, but in effervescent or acidic formulations its reaction with acids must be taken into account.