Source: Health Products Regulatory Authority (IE) Revision Year: 2021 Publisher: GlaxoSmithKline Consumer Healthcare (Ireland) Limited, 12 Riverwalk, Citywest Business Campus, Dublin 24, Ireland
Pharmacotherapeutic group: Calcium carbonate and cholecalciferol
ATC Code: A12AX
Vitamin D supplementation corrects an insufficient vitamin D intake. It increases the intestinal absorption of calcium. The optimal vitamin D dose in older subjects is 500-1000 I.U. per day. Calcium supplementation balances a dietary calcium deficiency. The usual calcium requirement of older people is 1500 mg/day. Vitamin D and calcium supplementation correct secondary senile hyperparathyroidism.
An 18-month, double-blind, placebo-controlled study carried out in 3270 women living in institutions, aged 84 Ā± 6 years and receiving a vitamin D3 supplement (800 IU/day) and calcium phosphate (corresponding to 1200 mg/day of elemental calcium), showed a significant decrease in PTH secretion. After 18 months, following an “intention to treat” (ITT) analysis, 80 hip fractures were observed in the calcium-vitamin D3 group and 110 hip fractures in the placebo group (p=0.004). In a follow-up study after 36 months, 137 women with at least one fracture of the hip were observed in the calcium-vitamin D3 group (n=1176) versus 178 women in the placebo group (n=1127) (pā¤0.02).
In the stomach, calcium carbonate releases calcium ions depending upon pH. The amount of calcium absorbed by the gastrointestinal tract is in the order of 30% of the ingested dose.
99% of calcium is stored in the hard matter of bones and teeth. The remaining one percent is found in intra and extracellular liquids. Approximately 50% of total blood calcium is found in the physiologically active ionised form, of which approximately 10% in complexes with citrate, phosphate or other anions with 40% remaining bound to proteins, mainly albumin.
Calcium is eliminated in the faeces, urine and in sweat. Kidney excretion depends on glomerular filtration and on calcium reabsorption by the tubules.
Vitamin D is easily absorbed by the small intestine.
Cholecalciferol and its metabolites circulate in the blood, linked to a specific alpha globulin. Cholecalciferol is metabolised in the liver by hydroxylation to its active form, 25-hydroxycholecalciferol. It is then metabolised in the kidneys to 1,25-dihydroxycholecalciferol. 1,25-dihydroxycholecalciferol is the metabolite responsible for the increase in calcium absorption. The vitamin D3 that is not metabolised is stored in adipose and muscle tissue.
Vitamin D3 is excreted via the faeces and urine.
Calcium carbonate and cholecalciferol did not show mutagenic potential in vitro (Ames test).
A teratogenic effect has been observed in animal studies at very much higher doses than human therapeutic doses.
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