Calcium citrate

Absorption

The percentage of calcium absorbed varies inversely with intake . Tmax of about 3.5-5h varying with formulation .

Toxicity

Patients taking more than 4g of calcium a day are at risk of hypercalcemia and metabolic alkalosis . Chronic intake of calcium supplements is associated with adverse gastrointestinal symptoms such as constipation and flatulence .

Description

Calcium citrate is the calcium salt of citric acid. It is commonly used as a food additive (E333), usually as a preservative, but sometimes for flavor. In this sense, it is similar to sodium citrate. Calcium citrate is also used as a water softener because the citrate ions can chelate unwanted metal ions. Calcium citrate is also found in some dietary calcium supplements (e.g. Citracal). Calcium makes up 21% of calcium citrate by weight.

Chemical properties

white powder or white to colourless crystals

Indications

For use as an over the counter calcium supplement.

Background

Calcium citrate is a salt typically used as a source of calcium in a variety of over the counter supplements.

Production Methods

Calcium citrate is an intermediate in the isolation of citric acid from the fermentation process by which citric acid is produced industrially. The citric acid in the broth solution is neutralized by calcium hydroxide, precipitating insoluble calcium citrate. This is then filtered off from the rest of the broth and washed to give clean calcium citrate.
The calcium citrate thus produced may be sold as-is, or it may be converted to citric acid using dilute sulfuric acid.

Definition

ChEBI: Calcium citrate is an organic calcium salt composed of calcium cations and citrate anions in a 3:2 ratio. It has a role as a nutraceutical, a food additive, a food preservative and a flavouring agent. It contains a citrate(3-).

Flammability and Explosibility

Non flammable

Pharmaceutical Applications

Calcium citrate is more easily absorbed (bioavailability is 2.5 times higher than calcium carbonate); it is easier to digest and less likely to cause constipation and gas than calcium carbonate. Calcium citrate can be taken without food and is more easily absorbed than calcium carbonate on an empty stomach. It is also believed that it contributes less to the formation of kidney stones. Calcium citrate consists of around 24% Ca²⁺, which means that 1000 mg calcium citrate contains around 240 mg Ca²⁺. The lower Ca²⁺ content together with the higher price makes it a more expensive treatment option compared to calcium carbonate, but its slightly different application field can justify this.

Biological Activity

In many individuals, bioavailability of calcium citrate is found to be equal to that of the cheaper calcium carbonate.However, alterations to the digestive tract may change how calcium is digested and absorbed. Unlike calcium carbonate, which is basic and neutralizes stomach acid, calcium citrate has no effect on stomach acid. Individuals who are sensitive to antacids or who have difficulty producing adequate stomach acid should choose calcium citrate over calcium carbonate for supplementation. According to recent research into calcium absorption after gastric bypass surgery , calcium citrate may have improved bioavailability over calcium carbonate in Rouxen- Y gastric bypass patients who are taking calcium citrate as a dietary supplement after surgery. This is mainly due to the changes related to where calcium absorption occurs in the digestive tract of these individuals.

Pharmacokinetics

Increases plasma calcium levels leading to a decrease in calcium flux and increase in calcium deposition into bone

Metabolism

Not Available