Hypoparathyroidism, Hypocalcaemia, Renal osteodystrophy, Hypophosphataemia, Rickets or osteomalacia Hypercalcaemia, metastatic calcification, hyperphosphataemia (except when occurring with hypoparathyroidism), hypermagnesaemia.

Vitamin in bone formation, Vitamin-D preparations

The first step involved in the activation of vitamin D3 is a 25-hydroxylation which is catalysed by the 25-hydroxylase in the liver and then by other enzymes. The mitochondrial sterol 27-hydroxylase catalyses the first reaction in the oxidation of the side chain of sterol intermediates. The active form of vitamin D3 (calcitriol) binds to intracellular receptors that then function as transcription factors to modulate gene expression. Like the receptors for other steroid hormones and thyroid hormones, the vitamin D receptor has hormone-binding and DNA-binding domains. The vitamin D receptor forms a complex with another intracellular receptor, the retinoid-X receptor, and that heterodimer is what binds to DNA. In most cases studied, the effect is to activate transcription, but situations are also known in which vitamin D suppresses transcription. Calcitriol increases the serum calcium concentrations by: increasing GI absorption of phosphorus and calcium, increasing osteoclastic resorption, and increasing distal renal tubular reabsorption of calcium. Calcitriol appears to promote intestinal absorption of calcium through binding to the vitamin D receptor in the mucosal cytoplasm of the intestine. Subsequently, calcium is absorbed through formation of a calcium-binding protein.

Administration: Administration Should be taken with food. Adult Dose: Adult: PO Hypocalcaemia; Hypoparathyroidism; Hypophosphataemia; Renal osteodystrophy; Rickets or osteomalacia Initial: 1 mcg/day. Maintenance: 0.25-1 mcg/day. Elderly: 0.5 mcg daily. Child Dose: Child: PO: Premature infants and neonates: 0.05-0.1 mcg/kg daily; <20 kg: 0.05 mcg/kg daily.

Thiazides may increase the risk of hypercalcaemia. Some antiepileptics e.g. carbamazepine, phenobarbital, phenytoin and primidone may increase vitamin D requirements. Rifampicin, isoniazid and corticosteroids may reduce the efficacy of vitamin D.

Hypercalcaemia, metastatic calcification, hyperphosphataemia (except when occurring with hypoparathyroidism), hypermagnesaemia.

Anorexia, nausea, vomiting, diarrhoea, lassitude, polyuria, sweating, headache, thirst, vertigo, pruritus, rash, urticaria. Hypercalcaemia, hypercalciuria and ectopic calcification. In case of renal impairment, hyperphosphataemia. In hypercalcaemic dialysis patients, possibility of calcium influx from the dialysate should be considered.

FDA has not yet classified the drug into a specified pregnancy category.

Precaution: Pregnancy, lactation, renal impairment, infants, elderly. Monitor serum levels of calcium in patients with renal failure. Caution in hypercalciuria esp in those with history of renal calculi. Avoid in patients with hypersensitivity to inj. containing propylene glycol.

Keep below 30°C temperature, away from light & moisture. Keep out of the reach of children.

Vitamin in bone formation, Vitamin-D preparations

Alfacalcidol is a precursor of the active calcitriol. It does not require renal hydroxylation but requires 25-hydroxylation in the liver for conversion to calcitriol.

FDA has not yet classified the drug into a specified pregnancy category.