Vitamine D - Use
The daily requirement for vitamin D of an adult is about 5 to 10 micrograms of colecalciferol or ergosterolcorresponding to . 200 to 400 iu.
Vitamin D preparations are used to prevent and to cure rickets in children and osteomalacia in adults. In elderly, low dose of vitamin D could slow down the progression of osteoporosis.
The most used preparations are ergocalciferol = calciferol = vitamin D2 and colecalciferol = vitamin D3. The doses usually recommended are 400 to 1000 iu daily.
Calcitriol (Rocaltrol*) is used in the treatment of patients with renal osteodistrophy in which the last activation by hydroxylation is defective.
Alfacalcidol (Un-alfa *) corresponds to hydroxylated vitamin D3 in position 1. It is transformed into 1-25 (OH)2D3 in the body and is used in the treatment of rickets resistant tothe precursors of vitamin D.
Calcifediol( Dedrogyl*) being already hydroxylated does not require hepatic activation, however this one is seldom defective, evenin the event of hepatic insufficiency.
Calcipotriol (Daivonex *, Dovonex*) is used topically for the treatment of psoriasis.
Tacalcitol, derivative of vitamin D3, is used in local application for the treatment of the psoriasis.
Tacalcitol |
is another derivative of vitamin D3 |
Adverse effects
An excessive intake of vitamin D induces hypervitaminosis resulting in:
- general and digestive signs: tiredness, anorexia, vomiting, diarrhea, headache
- an hypercalcemia being able to inhibit growth during several months
- renal signs: polyuria, polydipsy, nocturia, proteinuria
- cardiovascular signs: hypertension, arterial calcifications.
Hypervitaminosis D in pregnant women can cause in the fetus development of an aortic stenosis with suppression of parathyroid activity.
The treatment of hypervitaminosis consists of discontinuation of vitamin D, decrease of calcium intake, intake of fluid and possible administration of glucocorticoids.
Interactions between vitamin D and certain drugs, in particular anticonvulsants, phenobarbital and phenytoin, were described: the treated epileptics present symptoms of rickets and osteomalacia with decrease of the plasma concentration of calcifediol, because the drugs induce an acceleration of vitamin D catabolism.
Even if calcipotriol has little activity on calcium metabolism, applied on large surface it caused hypercalcemia and hypercalciuria.
Notice
Vitamin D was used at high concentrations as a rodenticide.
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