Calcium Citrate: characteristic, mechanism of action, application

The bulk of Ca in the adult body (about 99%) is contained in bone tissue in the composition of hydroxyapatite crystals. In the serum of most mammals, the calcium concentration is about 3 mmol / l (10-12 mg / 100 ml) and is constant. Daily fluctuations of this constant do not exceed 3-5%. Ca is necessary for the normal functioning of the nervous system. In the neuromuscular synapses, calcium ions contribute to the release of acetylcholine and its combination with the choline receptor, and in the presence of an excess of acetylcholine, cholinesterase, an enzyme that hydrolyses acetylcholine, is activated.

The Ca ions, contained in the sarcoplasmic reticulum, promote the interaction of actin and myosin, that is, the contraction of the muscle fiber. This effect is carried out in the presence of magnesium ions.

Calcium ions activate enzymatic processes at the initial stages of blood clotting - with the formation of thromboplastin and thrombin. The binding of Ca ions in plasma with oxalates or citrates prevents coagulation of the blood.

Recently, a unique role of calcium in the vital activity of cells has been proved, in the cytoplasm of which its concentration does not exceed 10-6 mol. At the cellular level, six basic physiological processes are distinguished, which depend on the concentration of Ca ions:

A) motor activity of cells (contraction of muscles);

B) excitability of cells that are capable of generating electrostatic action potential (muscle tone, nerve impulse, photoreception, cardiac contraction);

C) the release of substances that are synthesized in the cell (secretion of hormones and neurotransmitters);

D) incorporation into the cell of soluble substances by vesiculation (phagocytosis);

E) intracellular metabolism (synthesis of glucose, lipolysis, etc.);

E) reproduction of cells (fertilization and mitosis of eggs, motility of spermatozoa).

Ca ions together with specific proteins provide elasticity and hardness of bone tissue. Modern medicine uses many drugs with calcium ions (glucanate, citrate, chloride, lactate, carbonate, phosphate, etc.). Calcium citrate is of particular importance. The main stage of calcium release from its complexes (phosphates, sulfates, chlorides) with organic and mineral components of food occurs in the stomach under the influence of chloride acid and proteolytic enzymes. Carbonic and phosphoric acid calcium salts dissociate in the acidic environment of the stomach, and calcium in ionized form or in combination with soluble chelates enters the small intestine. Therefore, in conditions of reduced secretory function of the stomach, the availability of Ca for absorption is insufficient, which can become one of the reasons for the deficiency of this element in the body. Calcium citrate is best dissolved in the acidic environment of the stomach. Ionized calcium easily penetrates biological membranes, even through the placental barrier. The main part (about 80%) of calcium is excreted from the body with a fecal mass, with about 20% of urine output. Due to the fact that calcium citrate, or rather, citrate salt, helps to reduce oxalate in urine, the use of the drug does not lead to the formation of kidney stones.

It was found that during the night, the release of mineral salts from the body is activated. Therefore, doctors recommend taking calcium citrate after dinner or in the evening. A negative correlation was found between the dose of the drug and the pharmaceutical activity of calcium. What does it mean? Calcium citrate is better absorbed by the body in small doses. Therefore, it is best to take the drug several times a day. For each age group physiological norms of calcium intake are established. Calcium preparations are prescribed with both preventive and therapeutic (rickets, osteoporosis, osteomalacia, for strengthening tooth enamel) purpose. Potassium citrate is prescribed for heart failure, hypertension, for the normalization of acid-base and water-salt balances in the body.