Alkali citrate (also known as alkaline citrate) is an inhibitor of kidney stones. It refers to a combination of citrate salts and an alkali substance, typically a form of sodium, potassium, or calcium that makes the solution alkaline. It is commonly used in various applications, including in medicine, food, and chemistry. It is used to increase urine citrate levels – this prevents calcium oxalate stones by binding to calcium and inhibiting its binding to oxalate. It is also used to increase urine pH (alkalinize urine) – this prevents uric acid stones and cystine stones (which form in cystinuria).
It is different from citric acid which is citrate bonded by hydrogen ions (or protons) making it acidic. Citric acid does not alkalinize urine as alkali citrate does. Alkali citrate replaces the protons with a non-acid positively charged ion like sodium, potassium or magnesium.
- Medical Use: Alkali citrate solutions, such as sodium citrate or potassium citrate, are often used to treat conditions like kidney stones or to manage urinary pH. They help to alkalize the urine, preventing the formation of acidic crystals and facilitating the dissolution of certain types of kidney stones. It’s also used as an anticoagulant in blood collection, particularly in the prevention of clotting during transfusions or laboratory procedures.
- Food and Beverage: Sodium citrate (a type of alkali citrate) is commonly used in food products as an acidity regulator, emulsifying agent, or preservative. It’s often found in processed cheese, soft drinks, and other processed foods to stabilize pH levels.
- Chemistry: In laboratory settings, alkali citrate solutions may be used to control pH or as a buffer in chemical reactions. For instance, it’s often used in various buffers for biochemical or enzymatic processes.
Biological effects
Alkaline citrates are used to prevent recurrent calcium stone formation. This is one of the major types of kidney stones. The citrate salts can increase urine citrate, which binds with urine calcium, reduces supersaturation of calcium salts, and inhibits crystal formation. This helps prevent kidney stones.
Oral alkali supplementation can also slow the rate of kidney function decline and “potentially reduce the risk of end stage kidney disease (ESKD) in patients with chronic kidney disease (CKD) and metabolic acidosis.”
The compound also raises urine pH. When citrate is metabolized by the liver, it essentially generates bicarbonate, an important buffer. This reduces uric acid supersaturation and prevents uric acid stones and cystine stones.
Occurrences
- Alkali citrates are not typically found in nature in their pure form, as they are synthetic compounds. However, they are derived from citric acid, a naturally occurring substance.
- Source of Citric Acid: Citric acid is found in citrus fruits such as lemons, oranges, and limes, where it plays a role in the metabolism of plants. It is also found in small amounts in other fruits, certain vegetables, and some fermented products.
- Industrial Production: Alkali citrates are produced through the neutralization of citric acid with an alkali metal hydroxide (e.g., sodium hydroxide or potassium hydroxide). This process is commonly done in laboratories, pharmaceutical production, and food manufacturing.
Biological and Food Applications
In biological systems, alkali citrates are used as part of blood anticoagulants (e.g., sodium citrate is used in blood collection and preservation). They also serve as flavor enhancers, acidity regulators, and preservative agents in foods and beverages. The production of soft drinks, candies, and jams often utilizes alkali citrates.
Use in Pharmaceuticals: Alkali citrates are used in medicine to treat conditions like kidney stones (potassium citrate) and to adjust the pH of urine. Sodium citrate is also found in effervescent tablets and solutions.
Environmental and Industrial Applications: Alkali citrates are used in some cleaning and detergent formulations due to their ability to break down mineral deposits and scale. Their buffering properties make them useful in various chemical and industrial processes.
