Products
Calcium carbonate is commercially available as a drug in the form of tablets, capsules, effervescent tablets, chewable tablets, lozenges, and oral suspension, among others. Some products are combination preparations, for example with vitamin D3 or other antacids.
Structure and properties
Calcium carbonate (CaCO
3
, M
r
= 100.1 g/mol) exists in pharmacopoeia quality as a white to almost white powder that is practically insoluble in water. In nature, it is found, for example, in limestone (a sedimentary rock), in the minerals calcite (calcite) and aragonite, in marble, in chalk, in mussel shells, eggshells, snail shells, and in pearls. Calcium carbonate is also called lime. Hard water forms from calcium carbonate in rocks, which is mixed with CO
2
-saturated water comes into contact. This produces the soluble calcium hydrogen carbonate (Ca(HCO
3
)
2
). Hard water, conversely, can lead to calcium carbonate deposits. When exposed to heat, calcium carbonate forms calcium oxide, a burnt lime, which reacts with water in a highly exothermic reaction to form slaked lime calcium hydroxide.
Effects
Calcium carbonate is a base that neutralizes stomach acid. The carbonate is protonated by the acid to form carbonic acid, which rapidly decomposes to carbon dioxide and water:
- 2 HCl (hydrochloric acid) + CaCO
3
(calcium carbonate) CaCl
2
(calcium chloride) + H
2
O (water) + CO
2
(carbon dioxide) ↑
The formation of calcium chloride in the stomach is also the basis for use in hyperphosphatemia. Calcium chloride forms insoluble calcium phosphate salts with dietary phosphate ions, which are excreted in the stool. In this way, the phosphate load is reduced. Calcium is one of the most important minerals and is important, among other things, for the formation of bones and teeth, for the conduction of nerve cells, the musculature, the heart and blood clotting.
Fields of application
- For the prevention and treatment of calcium deficiency (calcium substitution).
- For the prevention and treatment of osteoporosis (calcium substitution).
- For the treatment of stomach burns and acid regurgitation (gastroesophageal reflux).
- As a phosphate binder for the treatment of hyperphosphatemia in chronic renal failure in patients on dialysis.
Calcium carbonate is also used as a pharmaceutical excipient, for example, for the production of tablets.
Dosage
According to the professional information. Dosage depends on the product and the indication. The usual daily dose for adults is in the range of 500 to 1500 mg of calcium. Antacids should not be overdosed.
Contraindications
Contraindications include (selection):
- Hypersensitivity
- Elevated calcium levels (hypercalcemia)
- Kidney stones
- Children and adolescents (depending on the preparation).
For complete precautions, see the drug label.
Interactions
Calcium may inhibit the absorption of other drugs. This is true, for example, of certain antibiotics such as the tetracyclines and the quinolones, as well as iron, levothyroxine, and bisphosphonates. A sufficient time interval of at least two to three hours must be observed. Calcium may further potentiate the effects of cardiac glycosides, and oxalic acid may decrease calcium uptake. Other interactions have been described, for example, with thiazides and vitamin D.
Adverse effects
Because carbon dioxide gas is formed on contact with stomach acid, calcium carbonate may cause a distended stomach and belching. Other possible adverse effects include constipation, flatulence, nausea, abdominal pain, diarrhea, and reactive gastric acid secretion (acid rebound). Overdose can lead to potentially dangerous hypercalcemia.
