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1,25-Dihydroxycholecalciferol: Wikis

  

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1,25-Dihydroxycholecalciferol
Systematic (IUPAC) name
(1R,3S)- 5-[2-[(1R,3aR,7aS)-1- [(2R)-6-hydroxy-6-methyl-heptan-2-yl]-
7a-methyl-2,3,3a,5,6,7-hexahydro-1H- inden-4-ylidene]ethylidene]-
4-methylidene-cyclohexane-1,3-diol
Identifiers
CAS number 32222-06-3
ATC code A11CC04 D05AX03
PubChem 134070
DrugBank APRD00246
ChemSpider 118219
Chemical data
Formula C27H44O3 
Mol. mass 416.64 g/mol
SMILES eMolecules & PubChem
Pharmacokinetic data
Metabolism Renal
Half life 5–8 hours
Excretion Renal
Therapeutic considerations
Pregnancy cat. B3 (Au), C (U.S.)
Legal status S4 (Au), POM (UK)
Routes Oral, IV, topical
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Calcitriol (INN) (pronounced /ˌkælsɨˈtraɪɒl/, /ˌkælˈsɨtriːɒl/) or 1,25-dihydroxycholecalciferol is the hormonally active form of vitamin D with three alcohol groups (abbreviated 1,25-(OH)2D3). It increases the level of calcium in the blood by (1) increasing the uptake of calcium from the gut into the blood, (2) decreasing the transfer of calcium from blood to the urine by the kidney, and (3) increasing the release of calcium into the blood from bone.

Contents

Nomenclature

Calcitriol usually refers specifically to 1,25-dihydroxycholecalciferol, but may also sometimes include 24,25-dihydroxycholecalciferol (when specified).

Because cholecalciferol already has one alcohol group, only two are further specified in the nomenclature.

Calcitriol is marketed under various trade names including Rocaltrol (Roche), Calcijex (Abbott) and Decostriol (Mibe, Jesalis).

Production and function

Calcitriol is produced in the cells of the proximal tubule of the nephron in the kidneys by the action of the enzyme 25-hydroxyvitamin D3 1-alpha-hydroxylase which catalyzes the hydroxylation of 25-hydroxycholecalciferol (calcifediol).

The production of calcitriol is stimulated by a decrease in serum calcium (hypocalcemia) and/or increase in serum phosphate (PO43−) (hyperphosphatemia), as well as an increase in parathyroid hormone (PTH). Calcitriol production is also increased by prolactin, a hormone which stimulates lactogenesis (the formation of breast milk), a process which requires large amounts of calcium.

Calcitriol increases blood calcium levels by increasing absorption of calcium and phosphate from the gastrointestinal tract and increasing renal tubular absorption of calcium and phosphate. It can also increase blood calcium by acting in concert with, and facilitating the effect of PTH on bone resorption. Calcitriol also inhibits the release of calcitonin, a hormone which reduces blood calcium by counteracting the effects of PTH.

Many of the effects of calcitriol are mediated by the calcitriol receptor.

Metabolism

Calcitriol becomes calcitroic acid through the action of 24-hydroxylase. Calcitroic acid is excreted in the urine.

Medical use

Calcitriol is prescribed for:[1]

Calcitriol is also sometimes used topically in the treatment of psoriasis, however the evidence to support its efficacy is inconclusive.[2] The vitamin D analogue calcipotriol is more commonly used for psoriasis.

Adverse effects

The main adverse drug reaction associated with calcitriol therapy is hypercalcaemia – early symptoms include: nausea, vomiting, constipation, anorexia, apathy, headache, thirst, sweating, and/or polyuria). Compared to other vitamin D compounds in clinical use (cholecalciferol, ergocalciferol), calcitriol has a higher risk of inducing hypercalcaemia. However, such episodes may be shorter and easier to treat due to its relatively short half-life.[1]

See also

Additional images

References

  1. ^ a b Rossi S, editor. Australian Medicines Handbook 2006. Adelaide: Australian Medicines Handbook; 2006. ISBN 0-9757919-2-3
  2. ^ Calcitriol. In: Klasco RK, editor. Drugdex system. vol 128. Greenwood Village (CO): Thomson Micromedex; 2006.







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