Calcitriol¿¡ ´ëÇÑ Mechanism_Of_Action Á¤º¸ 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)2D 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)2D 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.
Pharmacology
Calcitriol¿¡ ´ëÇÑ Pharmacology Á¤º¸ Calcitriol, a pharmaceutical form of vitamin D, has anti-osteoporotic, immunomodulatory, anticarcinogenic, antipsoriatic, antioxidant, and mood-modulatory activities. Calcitriol has been found to be effective in the treatment of psoriasis when applied topically. Calcitriol has been found to induce differentiation and/or inhibit cell proliferation in a number of malignant cell lines including human prostate cancer cells. Vitamin D deficiency has long been suspected to increase the susceptibility to tuberculosis. The active form of Calcitriol, 1,25 (OH)2 D, has been found to enhance the ability of mononuclear phagocytes to suppress the intracellular growth of Mycobacterium tuberculosis. 1,25(OH)2D has demonstrated beneficial effects in animal models of such autoimmune diseases as rheumatoid arthritis. It has also been found to induce monocyte differentiation and to inhibit lymphocyte proliferation and production of cytokines, including interleukin IL-1 and IL-2, as well as to suppress immunoglobulin secretion by B lymphocytes. Vitamin D appears to demonstrate both immune-enhancing and immunosuppressive effects.
Calcitriol¿¡ ´ëÇÑ Biotransformation Á¤º¸ The first pathway involves 24-hydroxylase activity in the kidney; this enzyme is also present in many target tissues which possess the vitamin D receptor such as the intestine. The end product of this pathway is a side chain shortened metabolite, calcitroic acid. The second pathway involves the conversion of calcitriol via the stepwise hydroxylation of carbon-26 and carbon-23, and cyclization to yield ultimately 1a,25R(OH)2-26,23S-lactone D3. The lactone appears to be the major metabolite circulating in humans.
Toxicity
Calcitriol¿¡ ´ëÇÑ Toxicity Á¤º¸ LD50 (oral, rat) = 620 ¥ìg/kg; LD50 (intraperitoneal, rat) > 5 mg/kg; Overdose evident in elevated blood calcium levels causing symptoms of anorexia, nausea and vomiting, polyuria, polydipsia, weakness, pruritus, and nervousness, potentially with irreversible calcification of soft tissue in the kidney and liver.
Drug Interactions
Calcitriol¿¡ ´ëÇÑ Drug_Interactions Á¤º¸ Not Available
Calcitriol¿¡ ´ëÇÑ Description Á¤º¸ Calcitriol or 1,25-dihydroxycholecalciferol (abbreviated 1,25-(OH)2D3) 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 D3 1-alpha-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.
The database contains the following fields: The generic name of each chemical For module A10 (liver enzyme composite module): Overall activity category for each compound (A for active, M for marginally active, or I for inactive) based on the number of active and marginally active scores for each compound at the five individual endpoints (see research article for full description of method) Number of endpoints at which each compound is marginally active (M) Number of endpoints at which each compound is active (A) For modules A11 to A15 (alkaline phosphatase increased, SGOT increased, SGPT increased, LDH increased, and GGT increased, respectively): Overall activity category for each compound (A for active, M for marginally active, or I for inactive) based on the RI and ADR values (see the research article for full description of method) Number of ADR reports for each compound, given as <4 or ¡Ã4 Reporting Index value for each compound, except where no shipping units were available (NSU) Group 1 comprises of compounds for which ADR data were available for the first five years of marketing, so when no ADR reports were listed during this period the compounds were evaluated as inactive. Group 2 comprises of compounds for which a 'steady state' period of ADR data were available (1992-1996). In cases where no ADR reports were filed during this period, the compounds were scored as 'NA' (data not available) since they may have had one or more ADR reports during their first five years of marketing which should not be negated by a lack of ADR reports during the steady-state period. CALCITRIOL [GGT Increase] [Composite Activity] (Score)I (Marginal) 0 (Active) 0