cholecalciferol
vitamin D· Brands: Vigantol, Dekristol, Fultium, Ostevit-DIMPO
Mechanism of action
Cholecalciferol is a fat-soluble vitamin D3. It is hydroxylated in the liver to calcidiol, which is the main circulating form, and then in the kidney to calcitriol, the active hormone. Calcitriol binds to the vitamin D receptor, modulating gene transcription. This increases intestinal absorption of calcium and phosphate, reduces renal calcium excretion, and promotes bone mineralization. It also has immunomodulatory effects.
Pharmacokinetics
Cholecalciferol is absorbed in the small intestine, with bile salts and dietary fat facilitating uptake. It is stored in adipose tissue and the liver. The initial hydroxylation in the liver produces calcidiol, which has a long half-life of about 2 to 3 weeks. Renal hydroxylation yields calcitriol, the active metabolite. Excretion occurs mainly through bile and faeces, with minor renal elimination.
Indications & dosing
Prevention of vitamin D deficiency
Recommended daily intake for adults at risk.
- adult · PO: 400–800 IU daily · Recommended daily intake for adults at risk.
Treatment of vitamin D deficiency
For 8 weeks, then maintenance 800-1,000 IU daily.
- adult · PO: 50000 IU once weekly · For 8 weeks, then maintenance 800-1,000 IU daily.
Prevention of vitamin D deficiency in children
For infants and children, especially if breastfed.
- pediatric · PO: 400 IU daily · For infants and children, especially if breastfed.
Treatment of vitamin D deficiency in children
For 8-12 weeks, then maintenance dose.
- pediatric · PO: 1000–5000 IU daily · For 8-12 weeks, then maintenance dose.
Contraindications & precautions
- Hypercalcaemia · Vitamin D increases calcium absorption, worsening hypercalcaemia.
- Hypervitaminosis D · Excess vitamin D stores may cause toxicity.
- Hypersensitivity to cholecalciferol · Allergic reactions can occur, including angioedema.
- Renal stones (calcium-based) · Increased calcium absorption may promote stone formation in susceptible individuals.
- Monitor serum calcium and 25-hydroxyvitamin D levels during therapy.
- Use with caution in renal impairment; high doses may cause hypercalcaemia.
- Use with caution in sarcoidosis, as vitamin D may increase calcitriol production.
- Use with caution in patients with a history of calcium-based renal stones.
- Pregnancy: low doses are safe; high doses should be avoided.
Adverse effects
- Hypercalcaemiaserious
- Hypercalciuriaserious
- Nausea
- Vomiting
- Headache
- Weakness
Renal & hepatic adjustment
- eGFR 0–29: Use with caution; monitor serum calcium regularly. Consider active vitamin D analogues for renal osteodystrophy.
Monitoring, pregnancy & toxicity
- Serum calcium · Baseline and at 1, 3 and 6 months of treatment, then 6-monthly in long-term therapy.
- 25-hydroxyvitamin D levels · After 3 months of treatment to assess response.
- Serum phosphate · In patients with renal impairment.
- Urinary calcium excretion · If hypercalciuria is suspected or with high-dose therapy.
- Pregnancy: Cholecalciferol is safe and recommended during pregnancy at appropriate doses for the prevention and treatment of vitamin D deficiency.
- Toxicity: Hypercalcaemia (nausea, vomiting, constipation, confusion, polyuria, polydipsia) · Stop cholecalciferol; rehydrate with IV saline; monitor serum calcium. Severe cases may require corticosteroids or bisphosphonates.
- Toxicity: Hypercalciuria and renal stones · Discontinue treatment; ensure adequate hydration; monitor renal function.
- Toxicity: Metastatic calcification · Stop vitamin D; supportive care; monitor calcium and renal function.
Clinical notes
Cholecalciferol is used to prevent and treat vitamin D deficiency, including rickets and osteomalacia, and as an adjunct in osteoporosis. It is also used in hypoparathyroidism and renal osteodystrophy. Dose varies with deficiency severity and purpose, from daily low doses (e.g., 800 to 2000 IU) to higher weekly or monthly regimens for severe deficiency. Monitor serum 25-hydroxyvitamin D to guide therapy. Caution in hypercalcemia, sarcoidosis, and renal impairment. Absorption may be impaired in fat malabsorption states.
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BNF; local formulary