Adults

Typically 500 mg to 1200 mg elemental calcium per day, divided into 1 to 3 doses. For osteoporosis, 500-1000 mg daily. Acical 500 mg: 1-2 tablets daily.

Elderly

Same as adult dosage, but often higher doses are required due to decreased absorption. Consult physician.

Renal_impairment

Use with caution and monitor calcium levels. Dosage adjustment may be necessary to avoid hypercalcemia.

Onset

Effects on serum calcium levels are relatively rapid, typically within 1-2 hours after administration.

Excretion

Unabsorbed calcium is excreted in feces. Absorbed calcium is primarily excreted via the kidneys (glomerular filtration and tubular reabsorption) and to a lesser extent via bile and sweat.

Half life

The half-life of calcium in the bloodstream is complex due to its constant exchange with bone, but the elimination half-life from plasma is generally short, within hours.

Absorption

Approximately 20-30% of ingested calcium carbonate is absorbed, primarily in the duodenum and proximal jejunum, through active and passive transport mechanisms. Absorption is enhanced by Vitamin D.

Metabolism

Calcium itself is not metabolized in the traditional sense; it is a mineral. It's incorporated into bones or maintained in the free ion form.

Bisphosphonates

Calcium can reduce the absorption of bisphosphonates (e.g., alendronate). Administer calcium at least 30-60 minutes after bisphosphonates.

Thyroid hormones

Calcium can reduce the absorption of levothyroxine. Administer calcium at least 4 hours after thyroid hormones.

Thiazide diuretics

Can decrease urinary calcium excretion, potentially leading to hypercalcemia.

Tetracyclines & Quinolones

Calcium can chelate these antibiotics, reducing their absorption. Administer calcium at least 2-4 hours before or after these antibiotics.