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Uses

Hypoparathyroidism and Pseudohypoparathyroidism

Management of hypocalcemia and its clinical manifestations in patients with postsurgical or idiopathic hypoparathyroidism and pseudohypoparathyroidism†.

Familial Hypophosphatemia

Treatment of familial hypophosphatemia (vitamin D resistant rickets).

Because the large doses of ergocalciferol needed in this disorder often cause toxicity and persistent hypercalcemia, some clinicians prefer dihydrotachysterol or calcitriol † and phosphate supplements.

Familial Hypophosphatemia associated with Fanconi syndrome

Has been used with treatment of acidosis, to manage hypophosphatemia associated with Fanconi syndrome†.

Nutritional Rickets or Osteomalacia

Has been used in the treatment of nutritional rickets or osteomalacia†.

Also has been used in the management of tetany and rickets in vitamin D-deficient infants†.

Anticonvulsant-induced Rickets and Osteomalacia

Has been used in the treatment of rickets or osteomalacia secondary to long-term high-dose anticonvulsant therapy†.

May be used in the prevention of anticonvulsant-induced rickets and osteomalacia† (particularly in those receiving 2 or more anticonvulsants and who have inadequate nutrition and exposure to UV light such as institutional patients). Adequate vitamin D supplementation usually prevents associated osteomalacia.

Vitamin D-dependent Rickets

Has been used in the treatment of vitamin D-dependent rickets†.

Renal Osteodystrophy or Hypocalcemia Secondary to Chronic Renal Disease

Has been used in the treatment of early renal osteodystrophy†.

Osteoporosis

Has been used in conjunction with calcium in the treatment of osteoporosis†.

Dietary and Replacement Requirements

Adequate intake (AI) of vitamin D is needed to support calcium metabolism and bone health, particularly in the young and old, and thus prevent rickets in children and osteomalacia in adults.

In addition, AI of vitamin D prevents secondary hyperparathyroidism and associated abnormalities in calcium metabolism that can result in porotic bone changes.

Dosage and Administration

General

• Measure serum calcium, phosphorus, and BUN concentrations every 2 weeks or more frequently if needed.
• The manufacturers recommend radiographic examination of the bones in patients with familial hypophosphatemia or hypoparathyroidism every month until the condition stabilizes and is corrected.
• Adequate dietary calcium is necessary for clinical response to vitamin D therapy.

Administration

Usually administered orally once daily. May be administered IM in some patients (e.g., those with GI, liver, or biliary disease associated with malabsorption of vitamin D analogs); manufacturers state that these patients should not receive oral ergocalciferol.

Dosage

Activity of ergocalciferol may be expressed in terms of USP or International Units (IU, units) which are equivalent; 1 unit of vitamin D equals the biologic activity of 25 ng.

Each mg of ergocalciferol is equivalent to 40,000 USP units; each mcg of the drug is equivalent to 40 USP units.

Dosage depends on nature and severity of hypocalcemia. Individualize dosage to maintain serum calcium concentrations of 9–10 mg/dL.

Pediatric Patients

Hypoparathyroidism and Pseudohypoparathyroidism

Oral

1.25–5 mg daily with calcium supplements.†

Prolonged administration of dosages >2.5 mg daily may increase risk of toxicity; gradually decrease dosage as serum calcium concentrations approach normal. †

Familial Hypophosphatemia (Vitamin D-Resistant Rickets)

Oral

Initially, 1–2 mg daily with phosphate supplements.

May increase daily dosage in 250- to 500-mcg increments at 3- to 4-month intervals until an adequate response is obtained.

After growth is complete, may reduce dosage.

Familial Hypophosphatemia associated with Fanconi syndrome

Dosages of 625 mcg to 1.25 mg daily have been used. †

Nutritional Rickets and Osteomalacia

Normal GI Absorption

Oral

25 mcg daily has been used and resulted in normal serum calcium and phosphate concentrations in about 10 days, radiographic evidence of bone healing within 2–4 weeks, and complete healing within 6 months.†

50–125 mcg daily has been used for 6–12 weeks for more prompt healing.†

May discontinue drug, if healing has occurred with therapy and correction of diet. †

Malabsorption

Oral

Children: 250–625 mcg daily. †

A single 7.5- to 15-mg dose (in oil solution) has been given when compliance was not predictable.†

Infants with tetany and rickets: Initially administer calcium to control tetany, then ergocalciferol 50–125 mcg daily (until bones have healed) or 250 mcg daily for about 3 weeks.†

Vitamin D-dependent Rickets

Oral

75–125 mcg daily; some may require up to 1.5 mg daily. †

Renal Osteodystrophy or Hypocalcemia Secondary to Chronic Renal Disease

Oral

0.1–1 mg daily has been used to maintain normal serum calcium concentrations. †

Dietary and Replacement Requirements

The AI of vitamin D (in terms of cholecalciferol or ergocalciferol) to prevent rickets in healthy children is 5 mcg (200 units) daily.In breast-fed or formula-fed infants up to 6 months of age who have habitual small doses of sunshine, supplemental vitamin D is not necessary. In children 2–18 years of age with regular sun exposure, dietary supplementation usually not necessary; however, to cover the needs of all children, regardless where they live supplementation is recommended.

Adults

Hypoparathyroidism and Pseudohypoparathyroidism

Oral

625 mcg to 5 mg (up to 10 mg) daily with calcium supplements and/or IM or IV PTH.†

Prolonged administration of dosages >2.5 mg daily may increase risk of toxicity; gradually decrease dosage as serum calcium concentrations approach normal. †

Familial Hypophosphatemia (Vitamin D-resistant Rickets)

Oral

250 mcg to 1.5 mg (up to 12.5 mg) daily with phosphate supplements (usually 1–2 g of elemental phosphorus daily) to maintain serum phosphorus concentrations of at least 3 mg/dL.

Familial Hypophosphatemia associated with Fanconi syndrome

Dosages of 1.25–5 mg (up to 10 mg) daily have been used along with treatment for acidosis.†

Nutritional Rickets and Osteomalacia

Normal GI Absorption

Oral

25 mcg daily has been used resulting in normal serum calcium and phosphorus concentrations in about 10 days, radiographic evidence of bone healing within 2–4 weeks, and complete healing within 6 months.†

50–125 mcg daily has been used for 6–12 weeks for more prompt healing.†

May discontinue drug if healing has occurred with therapy and correction of diet. †

Severe Malabsorption

Oral

250 mcg to 7.5 mg. †

IM

250 mcg daily.†

Anticonvulsant-Induced Rickets and Osteomalacia

Oral

50 mcg to 1.25 mg daily. †

25 mcg daily or 250 mcg weekly has been used for prevention in those receiving long-term anticonvulsant therapy.†

Vitamin D-Dependent Rickets

Oral

250 mcg to 1.5 mg daily; some may require up to 12.5 mg daily.†

Prolonged administration of dosages >2.5 mg daily may result in toxicity. †

Renal Osteodystrophy or Hypocalcemia Secondary to Chronic Renal Disease

Oral

Initially, 500 mcg daily for early renal osteodystrophy, then adjust according to serum calcium concentration.†

May require 250 mcg to 7.5 mg daily (up to 12.5 mg daily) to maintain normal serum calcium concentrations.†

Osteoporosis

25–250 mcg daily or 1.25 mg 2 times weekly has been used with calcium and fluoride supplements.†

Dietary and Replacement Requirements

The AI of vitamin D (in terms of cholecalciferol or ergocalciferol) to prevent osteomalacia in healthy adults through 50 years of age is 5 mcg (200 units) daily, while for healthy adults 51–70 or >70 years of age, AI is 10 (400 units) or 15 mcg (600 units) daily, respectively.

Because exposure to sunlight is decreased markedly during the winter, adults can become vitamin D deficient. Therefore, to cover the needs of nearly all adults, supplementation is recommended. Pregnant and lactating women do not appear to have an increased requirement for vitamin D; however, daily vitamin D supplied by postnatal vitamins is not considered excessive.

Prescribing Limits

Pediatric Patients

Infants and children

Oral

Chronic daily ingestion of 25 mcg daily may result in hypervitaminosis D.

Adults

Oral

Chronic daily ingestion of 1.25–2.5 mg daily may result in hypervitaminosis D.