Vitamin d

VITAMIN D

Ajith.A

Fat soluble ,maintanence of plasma calcium and phosphate level , thermostabile

ISOFORMS• Vitamin D1• Vitamin D2 ( calciferol )• Vitamin D3 ( cholecalciferol )

ACTIVATION

7-Dehydro cholesterol

Ergosterol

UV light

CalciferolCholecalciferol

25- Hydroxy cholecalciferol

25-Hydroxy calciferol

Liver microsomes

Calcitriol1,25- Di Hydroxy

calciferol

Kidney Mitochondri

a

Active forms

ACTIONS

Calcitriol enhances absorption of calcium and phosphate from intestine.

It enhances resorption of calcium & phosphate from bone

Calcitriol enhances tubular reabsorption of calcium & phosphate in kidney

RDA 5µgm (200IU) or 400 IU/day if

there is no synthesis in bodyPREPARATIONS CALCIFEROL

as solution in oil, filled in gelatin capsules 25,000 and 50,000 IU caps.

CHOLECALCIFEROL

as granules for oral ingestion and oily solution for i.m injection

CALCITRIOL 0.25 – 1 µgm orally daily or on

alternate days 0.5 – 1 µgm I.v on alternate days

ALFACALCIDOL It is 1α – OHD3, a prodrug that is

rapidly hydroxylated in the liver to calcitriol 1-2µgm/day in adults for children<20 kg 0.5µgm/ day

DIHYDROTACHYSTEROL synthetic vit D2 analogue 0.25 – 0.5 mg/ day

PHARMACOKINETICS

Absorption Intestine in presence of bile salts

Storage Adipose tissues t1/2 1-18 Days Excretion Bile

Vit D DeficiencyInadequate absorption

Plasma calcium & phosphate

Secretion of PTH

Calcium mobilization from bone to restore plasma Ca

2+

Mineralization of bone fails in newly laid area & becomes soft

Rickets in children Oestomalacia in adults

USES

Prophylaxis (400 IU/ day) Treatment of nutritional Vit D deficiency (3000-4000 IU/day) or

(3,00,000 – 6,00,000 IU) orally or i.m once in 2-6 mnths

Metabolic rickets A.) Vit D resistant ricket administration of phosphate

with calcitriol or alfacalcidol

B.) Vit D dependent rickets administration of calcitriol or

alfacalcidolC.) Renal rickets alfacalcidol or calcitriol Senile or post menopausal

osteoporosis Vit D3 + Calcium Hypoparathyroidism Dihydrotachysterol is given Fanconi syndrome

HYPERVITAMINOSIS

> 50,000 IU/ dayExcess ingestion of vit D leads to• Hypercalcemia• Weakness• Fatigue• Vomiting

Diarrhoea sluggishness Polyuria Albuminuria Renal stones hypertension

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