Description

Vitamin D is an essential component in our body. Vitamin D functions by stimulating intestinal calcium and phosphorus absorption, by stimulating bone calcium mobilization, and by increasing renal reabsorption of calcium in the distal tubule. It helps to keep the bones and teeth healthy especially in the elderly and in those with deficiency of this Vitamin is evident due to familial or environmental reasons. The common source of this Vitamin is sunlight and this medicine acts as a Vitamin D3 supplement for those who may not receive all the Vitamin D3 they needed especially the housebound or living in nursing or residential homes.

Dosage

Oral

Nutritional deficiency

Adult: 10 mcg (400 units) daily. May also be given via IM inj.

Oral

Deficiency due to malabsorption states or liver diseases

Adult: Up to 1 mg (40,000 units) daily. May also be given via IM inj.

Oral

Hypocalcaemia caused by hypoparathyroidism

Adult: Up to 5 mg (2,00,000 units) daily. May also be given via IM inj.

Administration

May be taken with or without food.

Contraindications

Hypercalcaemia.
Rare evidence of Vitamin D toxicity.

Special precautions

Excessive intake may lead to development of hyperphosphataemia or hypercalcaemia. Infants, renal impairment or calculi, heart disease. Monitor plasma phosphate and calcium levels in pregnancy and lactation..

Adverse reactions

Hyperphosphataemia or hypercalcaemia (in excessive intake). Associated effects of hypercalcaemia include hypercalciuria, ectopic calcification, renal and CV damage.

Action

Vitamin D may have anti-osteoporotic, immunomodulatory, anticarcinogenic, antipsoriatic, antioxidant and mood-modulatory activities. Along with parathyroid hormone and calcitonin, regulate serum calcium conc.

Duration

Relatively prolonged duration of action.

Absorption

Well absorbed from the GI tract. Presence of bile is essential for adequate intestinal absorption. Hence, absorption may be decreased in patients with decreased fat absorption.

Distribution

Bound to a specific α-globulin. Can be stored in adipose and muscle tissue for long periods of time. Slowly released from storage sites and skin where it is formed in the presence of sunlight or UV light. May distribute into breast milk.

Metabolism

Hydroxylated in the liver by the enzyme Vitamin D 25-hydroxylase to form 25-hydroxycholecalciferol (calcifediol). Further hydroxylated in the kidneys by the enzyme Vitamin D1-hydroxylase to form the active metabolites 1,25-dihydroxycholecalciferol (calcitriol). Further metabolism also occurs in the kidneys, including the formation of the 1,24,25-trihydroxy derivatives.

Excretion

Mainly in the bile and faeces with only small amounts appearing in urine.