Adults

Typically 1-2 tablets daily, or as directed by physician. To be taken with water, preferably after meals.

Elderly

Same as adults, with careful consideration of renal function and existing medications.

Renal_impairment

Use with caution. Dosage adjustment may be required based on serum calcium and phosphate levels, and creatinine clearance.

Onset

Calcium and Vitamin D levels gradually increase over days to weeks with regular supplementation.

Excretion

Unabsorbed calcium is excreted in feces. Absorbed calcium is primarily excreted via the kidneys (urine). Vitamin D metabolites are primarily excreted in bile and feces, with some renal excretion.

Half life

The half-life of Vitamin D3 is approximately 15 hours, but its active metabolite (calcitriol) has a longer half-life (around 1-2 days). Calcium itself does not have a distinct plasma half-life, but its balance is maintained by regulatory hormones.

Absorption

Calcium carbonate is absorbed in the small intestine, with absorption enhanced by Vitamin D3. Cholecalciferol is readily absorbed from the small intestine, primarily in the presence of bile salts.

Metabolism

Cholecalciferol is metabolized in the liver to 25-hydroxycholecalciferol (calcidiol) and then in the kidneys to the active form, 1,25-dihydroxycholecalciferol (calcitriol).

Levothyroxine

Calcium can reduce levothyroxine absorption. Separate administration by at least 4 hours.

Bisphosphonates

Calcium can interfere with bisphosphonate absorption. Take calcium at a different time.

Corticosteroids

May reduce calcium absorption.

Cardiac glycosides

Increased risk of arrhythmias with hypercalcemia.

Thiazide diuretics

May reduce calcium excretion, leading to hypercalcemia.

Tetracyclines and Fluoroquinolones

Calcium can reduce absorption of these antibiotics. Administer at least 2 hours before or 4-6 hours after.