Adults

Typically, 1-2 tablets daily, or as directed by the physician. Can be taken as a single dose or divided doses.

Elderly

Same as adult dosage, but caution should be exercised in patients with renal impairment.

Renal_impairment

Use with caution and dose adjustment may be necessary. Regular monitoring of calcium levels is recommended. Consult a physician.

Onset

Effects on mineral levels can be seen within hours, but significant bone health benefits require long-term use.

Excretion

Calcium is primarily excreted via kidneys in urine and feces. Vitamin D metabolites are primarily excreted in bile and feces, with a minor amount in urine.

Half life

Calcium does not have a specific half-life but maintains a dynamic equilibrium. Vitamin D3 has a half-life of about 15 hours for the parent compound, while its active metabolite calcitriol has a half-life of 3-5 days.

Absorption

Calcium is absorbed primarily in the small intestine, with absorption varying based on dietary factors and vitamin D status. Vitamin D3 is absorbed in the small intestine, primarily in the jejunum, and transported via chylomicrons.

Metabolism

Calcium is not metabolized. Vitamin D3 is hydroxylated in the liver to 25-hydroxyvitamin D3 (calcifediol) and then in the kidneys to 1,25-dihydroxyvitamin D3 (calcitriol), its active form.

Levothyroxine

Calcium can reduce the absorption of levothyroxine. Administer at least 4 hours apart.

Bisphosphonates

Calcium can interfere with the absorption of bisphosphonates. Administer at least 30 minutes before or after calcium.

Thiazide diuretics

May increase the risk of hypercalcaemia by reducing calcium excretion.

Cardiac glycosides (e.g., digoxin)

Hypercalcaemia can potentiate the effects of cardiac glycosides, increasing the risk of cardiac arrhythmias.

Tetracycline and fluoroquinolone antibiotics

Calcium can chelate these antibiotics, reducing their absorption. Administer at least 2-3 hours apart.