DESCRIPTION
Calcitriol -Calcitriol or 1,25-dihydroxycholecalciferol (abbreviated 1,25-(OH)2-D3) is the active form of vitamin D found in the body (vitamin D3). Calcitriol is marketed under various trade names including Rocaltrol (Roche), Calcijex (Abbott) and Decostriol (Mibe, Jesalis). It is produced in the kidneys via 25-hydroxyvitamin D-1 a-hydroxylase by conversion from 25-hydroxycholecalciferol (calcidiol). This is stimulated by a decrease in serum calcium, phosphate (PO43-) and parathyroid hormone (PTH) levels. It regulates calcium levels by increasing the absorption of calcium and phosphate from the gastrointestinal tract, increasing calcium and phosphate reabsorption in the kidneys and inhibiting the release of PTH. Calcitriol is also commonly used as a medication in the treatment of hypocalcemia and osteoporosis.calcium carbonate -Calcium carbonate is an inorganic salt used as an antacid. It is a basic compound that acts by neutralizing hydrochloric acid in gastric secretions. Subsequent increases in pH may inhibit the action of pepsin. An increase in bicarbonate ions and prostaglandins may also confer cytoprotective effects. Calcium carbonate may also be used as a nutritional supplement or to treat hypocalcemia.
CHEMICAL FORMULA
Calcitriol -C27H44O3.calcium carbonate -CaCO3.vitamin k2-7 -
MECHANISM
Calcitriol -The mechanism of action of calcitriol in the treatment of psoriasis is accounted for by their antiproliferative activity for keratinocytes and their stimulation of epidermal cell differentiation. The anticarcinogenic activity of the active form of Calcitriol appears to be correlated with cellular vitamin D receptor (VDR) levels. Vitamin D receptors belong to the superfamily of steroid-hormone zinc-finger receptors. VDRs selectively bind 1,25-(OH)2-D3 and retinoic acid X receptor (RXR) to form a heterodimeric complex that interacts with specific DNA sequences known as vitamin D-responsive elements. VDRs are ligand-activated transcription factors. The receptors activate or repress the transcription of target genes upon binding their respective ligands. It is thought that the anticarcinogenic effect of Calcitriol is mediated via VDRs in cancer cells. The immunomodulatory activity of calcitriol is thought to be mediated by vitamin D receptors (VDRs) which are expressed constitutively in monocytes but induced upon activation of T and B lymphocytes. 1,25-(OH)2-D3 has also been found to enhance the activity of some vitamin D-receptor positive immune cells and to enhance the sensitivity of certain target cells to various cytokines secreted by immune cells.calcium carbonate -Calcium carbonate is a basic inorganic salt that acts by neutralizing hydrochloric acid in gastric secretions. It also inhibits the action of pepsin by increasing the pH and via adsorption. Cytoprotective effects may occur through increases in bicarbonate ion (HCO3-) and prostaglandins. Neutralization of hydrochloric acid results in the formation of calcium chloride, carbon dioxide and water. Approximately 90% of calcium chloride is converted to insoluble calcium salts (e.g. calcium carbonate and calcium phosphate).vitamin k2-7 -Vitamin K is necessary for the post-translational modification of a number of clotting factors and other proteins. It helps the blood to clot normally in the body.
ABSORPTION
Calcitriol -Rapidly absorbed from the intestine.calcium carbonate -Maximal absorption occurs at doses of 500 mg or less taken with food. Oral bioavailability depends on intestinal pH, the presence of food and dosage.
VOLUME DISTRIBUTION
calcium carbonate -Calcium is rapidly distributed taken up by skeletal tissues following absorption and distribution into extracellular fluids. Bone contains 99% of the body's calcium and the remaining 1% is approximately equally distributed between intracellular and extracellular fluids.
