Definition
ChEBI: The dihydrate of trisodium citrate.
Pharmaceutical Applications
Sodium citrate, as either the dihydrate or anhydrous material, is
widely used in pharmaceutical formulations.
It is used in food products, primarily to adjust the pH of
solutions. It is also used as a sequestering agent. The anhydrous
material is used in effervescent tablet formulations. Sodium citrate
is additionally used as a blood anticoagulant either alone or in
combination with other citrates such as disodium hydrogen citrate.
Therapeutically, sodium citrate is used to relieve the painful
irritation caused by cystitis, and also to treat dehydration and
acidosis due to diarrhea.
Biological Activity
Commonly used laboratory reagent
Biochem/physiol Actions
Sodium citrate can act as a buffering agent, resisting changes in pH. Used in blood collection tubes, the citrate chelates calcium ions in blood and thereby disrupts blood clotting. Citrate is a intermediate in the TCA cycle and fatty acid synthesis. Citrate is an allosteric modulator of acetyl-CoA carboxylase, the enzyme that regulates the conversion of acetyl-CoA to malonyl-CoA.
Safety
After ingestion, sodium citrate is absorbed and metabolized to
bicarbonate. Although it is generally regarded as a nontoxic and
nonirritant excipient, excessive consumption may cause gastrointestinal
discomfort or diarrhea. Therapeutically, in adults, up to
15 g daily of sodium citrate dihydrate may be administered orally, in
divided doses, as an aqueous solution to relieve the painful irritation
caused by cystitis.
Citrates and citric acid enhance intestinal aluminum absorption
in renal patients, which may lead to increased, harmful serum
aluminum levels. It has therefore been suggested that patients with
renal failure taking aluminum compounds to control phosphate
absorption should not be prescribed citrate- or citric acid-containing
products.
storage
Sodium citrate dihydrate is a stable material. Aqueous solutions
may be sterilized by autoclaving. On storage, aqueous solutions may cause the separation of small, solid particles from glass
containers.
The bulk material should be stored in an airtight container in a
cool, dry place.
Purification Methods
Crystallise the salt from warm water by cooling to 0o. [Beilstein 3 III 1100, 3 IV 1274.]
Incompatibilities
Aqueous solutions are slightly alkaline and will react with acidic
substances. Alkaloidal salts may be precipitated from their aqueous
or hydro-alcohol solutions. Calcium and strontium salts will cause
precipitation of the corresponding citrates. Other incompatibilities
include bases, reducing agents, and oxidizing agents.
Regulatory Status
GRAS listed. Accepted for use as a food additive in Europe.
Included in the FDA Inactive Ingredients Database (inhalations;
injections; ophthalmic products; oral solutions, suspensions, syrups
and tablets; nasal, otic, rectal, topical, transdermal, and vaginal preparations). Included in nonparenteral and parenteral medicines
licensed in the UK. Included in the Canadian List of Acceptable
Non-medicinal Ingredients.
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