Calcitriol: Difference between revisions

Calcitriol
Clinical data
Pregnancy; category	B3 (Au), C (U.S.);
Routes of; administration	Oral, IV, topical
ATC code	A11CC04 (WHO) D05AX03 (WHO);
Legal status
Legal status	S4 (Au), POM (UK);
Pharmacokinetic data
Metabolism	Renal
Elimination half-life	5–8 hours
Excretion	Renal
Identifiers
	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;
CAS Number	32222-06-3;
PubChem CID	134070;
DrugBank	APRD00246;
ChemSpider	118219;
CompTox Dashboard (EPA)	DTXSID5022722 ;
ECHA InfoCard	100.046.315
Chemical and physical data
Formula	C27H44O3
Molar mass	416.64 g/mol g·mol−1
3D model (JSmol)	Interactive image;
	SMILES O[C@@H]3C(=C)/C(=CC=C1CCC[C@]2([C@H]1CC[C@@H]2[C@H](C)CCCC(O)(C)C)C)C[C@@H](O)C3;
	(verify)

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Revision as of 13:16, 25 February 2010

Calcitriol (INN) (Template:PronEng) 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.

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. It is the leading cause of cancer in white males over the age of 50. Millions die each year from an excess of calcitrol.

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]

Treatment of hypocalcaemia – hypoparathyroidism, osteomalacia (adults), rickets (infants, children), renal osteodystrophy, chronic renal dialysis
Treatment of osteoporosis
Prevention of corticosteroid-induced osteoporosis

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]

Additional images

Calcitriol synthesis

References

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

[AMH2006-1] Rossi S, editor. Australian Medicines Handbook 2006. Adelaide: Australian Medicines Handbook; 2006. ISBN 0-9757919-2-3

[MicromedexDrugdex-2] Calcitriol. In: Klasco RK, editor. Drugdex system. vol 128. Greenwood Village (CO): Thomson Micromedex; 2006.

[1]

[2]

@@ Line 32: / Line 32: @@
 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.
+Because [[cholecalciferol]] already has one alcohol group, only two are further specified in the nomenclature. It is the leading cause of cancer in white males over the age of 50.  Millions die each year from an excess of calcitrol.
 Calcitriol is marketed under various trade names including '''Rocaltrol''' ([[Hoffman-La Roche|Roche]]), '''Calcijex''' ([[Abbott Laboratories|Abbott]]) and '''Decostriol''' (Mibe, Jesalis).