Adults

Typically, 1-2 tablets daily, or as directed by a physician. Best taken with meals.

Elderly

Same as adult dosage. However, kidney function should be monitored, and dose adjusted if necessary.

Renal_impairment

Use with caution. Dosage adjustment may be required based on the severity of renal impairment and serum calcium/phosphate levels. Consult a physician.

Onset

Clinical effects on bone density are gradual, typically observed over weeks to months of consistent use.

Excretion

Calcium is primarily excreted via feces, with a smaller amount via urine. Vitamin D metabolites are primarily excreted via the bile into the feces, with some renal excretion.

Half life

The half-life of cholecalciferol (Vitamin D3) is approximately 24 hours, but its active metabolite, calcitriol, has a half-life of 4-6 hours, and 25-hydroxyvitamin D has a much longer half-life (around 15 days).

Absorption

Calcium is absorbed primarily in the small intestine (jejunum and ileum), with absorption varying depending on intake. Vitamin D3 is absorbed from the small intestine, primarily the jejunum, requiring bile salts for absorption.

Metabolism

Vitamin D3 is hydroxylated in the liver to 25-hydroxyvitamin D3 (calcidiol), then further hydroxylated in the kidneys to 1,25-dihydroxyvitamin D3 (calcitriol), the active form.

Digoxin

Calcium may potentiate the effects and toxicity of digoxin.

Bisphosphonates

Calcium can interfere with the absorption of bisphosphonates. Take separately.

Thiazide diuretics

May increase the risk of hypercalcemia.

Tetracycline and Quinolone antibiotics

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